NOAA's National Centers for Environmental Information
Issued 12 November 2020
Please note that the values presented in this report are based on preliminary data. They will change when the final data are processed, but will not be replaced on these pages.
National Drought Highlights
- Based on the Palmer Drought Index, severe to extreme drought affected about 23% of the contiguous United States as of the end of October 2020, about the same as last month. About 18% of the contiguous U.S. fell in the severely to extremely wet categories.
- About 35% of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of October.
- On a broad scale, the 1980s and 1990s were characterized by unusual wetness with short periods of extensive droughts, the 1930s and 1950s were characterized by prolonged periods of extensive droughts with little wetness, and the first two decades of the 2000s saw extensive drought and extensive wetness (moderate to extreme drought graphic, severe to extreme drought graphic).
- A file containing the national monthly percent area severely dry and wet from 1900 to present is available for the severe to extreme and moderate to extreme categories.
- Historical temperature, precipitation, and Palmer drought data from 1895 to present for climate divisions, states, and regions in the contiguous U.S. are available at the Climate Division: Temperature-Precipitation-Drought Data page. These filenames begin with "climdiv".
U.S. Drought Monitor information is currently unavailable.
Detailed Drought Overview
The atmospheric circulation over North America during October 2020 began with a strong high pressure ridge over the western CONUS and trough over the East. Shortwave troughs and closed lows moved through the ridge at times during the month and deepened as they crossed the central CONUS. In addition, two tropical systems moved from the Gulf of Mexico across the southeastern CONUS (Hurricanes Delta and Zeta). The overall monthly circulation pattern consisted of a ridge along the West Coast and trough extending from Hudson Bay into the central CONUS. The tropical systems and surface lows and fronts associated with the upper-level troughs brought above-normal precipitation to parts of the Northwest, Northeast, Lower Mississippi to Ohio Valley, and Southeast. The western ridge kept most of the West drier than normal, while the dominant northwesterly flow aloft over central North America sent drier-than-normal Canadian air masses across the Plains. The preponderance of Canadian air masses gave the central CONUS a colder-than-normal month while ridging resulted in warmer-than-normal temperatures in the West and along the East Coast. The western ridge extended to Alaska where October averaged warmer than normal (except over the panhandle) and mostly drier than normal.
The continued hot temperatures in parts of the West and Southeast increased evapotranspiration (ET) (as seen by such indices as the ESI and EDDI), especially in the Southwest. The high ET exacerbated drought conditions for the areas that had below-normal precipitation (as seen, for example, by the Palmer Z Index and SPEI). The high ET and low precipitation further dried soils (as seen in satellite observations of soil moisture [SMOS; SPoRT LIS 0-10 cm depth, 0-40 cm depth, 0-100 cm depth, 0-200 cm depth, RSM], field reports [USDA NASS reports], and models [VIC, CPC, NLDAS, NASA GRACE surface soil moisture and root zone soil moisture, and Leaky Bucket]) and stressed vegetation (VegDRI, QuickDRI, VHI, NESDIS stressed and healthy vegetation). This was especially true across the West and Plains. Many of the streams and groundwater levels (GRACE satellite estimates, USGS observations) were low in these areas and parts of the Northeast. Dozens of large wildfires continued to burn across the West (wildfire maps for October 1, 6, 11, 18, 22, 30, 31), with 8.5 million acres burned nationwide so far this year, about 2 million more than the ten-year average, according to an October 31 National Interagency Coordination Center report. Reports received from the CoCoRaHS Condition Monitoring Resource (for September 29-October 5 and October 6-12, 13-19, 20-26, and October 27-November 2) included crop and livestock issues (reduced pasture, less water, animal stress, decreased stock weights), fire risk, air quality problems, dry lawns, forest impacts, and wildlife concerns, plus low wells in the Northeast.
As a result of these conditions, drought or abnormal dryness expanded or intensified across much of the West and Plains and parts of the Midwest, as well as Hawaii. Drought or abnormal dryness contracted in parts of the Northwest, Northeast, and a band from Oklahoma to the Great Lakes. Drought expansion exceeded contraction with the USDM-based national moderate-to-exceptional drought footprint across the CONUS rising from 42.6 percent at the end of September to 45.1 percent at the end of October (from 35.8 percent to 37.9 percent for the 50 States and Puerto Rico). According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 35.3 percent of the CONUS was in moderate to extreme drought at the end of October, about the same as the end of September.
Drought conditions at the end of October, as depicted on the November 3, 2020 USDM map, included the following core drought and abnormally dry areas:
- Moderate (D1) to extreme (D3) drought, with areas of exceptional (D4) drought, extended from the West Coast to Rocky Mountains and into the adjacent High Plains. The percent area of the West experiencing moderate to exceptional drought, according to USDM statistics, increased from 76.1 percent at the end of September to 77.7 percent at the end of October. The percent area of the West (from the Rockies to the West Coast) in moderate to extreme drought (based on the Palmer Drought Index) continued its increase to about 75.9 percent. Parts of Washington, northern Idaho, and Montana into northern Wyoming were wetter than normal, but most of the West was drier than normal for October with some areas record dry. The short-term dryness (October, September-October, August-October) just added to longer-term dryness (last 6, 9, 12, 24 months), making matters worse. Several states had a top ten dry October and record dry August-October and May-October, with Utah ranking driest on record for January-October. The excessive heat from California to the Four Corners States broke records and exacerbated the drought (October 2020 SPEI compared to SPI). The heat in October was a continuation of excessive heat which has lasted much of this year, and was especially extreme during the last three to six months. The heat of the last six months contributed to excessive evaporative demand in the Southwest as well as the Northeast.
- Drought continued to expand in the Plains. Abnormal dryness to extreme drought covered most of the central to northern Plains at the end of October, while moderate to exceptional drought persisted in western portions of the southern Plains with moderate drought developing in eastern Texas.
- In the Midwest, moderate to extreme drought continued in western Iowa, with areas of moderate drought lingering in Missouri, Minnesota, and the Ohio Valley states.
- In the Northeast, beneficial precipitation contracted drought and abnormally dry conditions, with moderate to extreme drought shrinking from 45.3 percent of the region at the end of September to 37.1 percent by the end of October. However, in spite of the recent precipitation, Connecticut still had the 12th driest May-October and Rhode Island the 14th driest.
- In Hawaii, moderate to extreme drought expanded to cover 71.8 percent of the state.
- Pockets of abnormal dryness and moderate drought persisted in Alaska.
- In the U.S.-Affiliated Pacific Islands (USAPI), abnormal dryness and drought disappeared in the Marshall Islands, but conditions worsened to exceptional drought in southern Micronesia at Kapingamarangi.
Palmer Drought Index
The Palmer drought indices measure the balance between moisture demand (evapotranspiration driven by temperature) and moisture supply (precipitation). The Palmer Z Index depicts moisture conditions for the current month, while the Palmer Hydrological Drought Index (PHDI) and Palmer Drought Severity Index (PDSI) depict the current month's cumulative moisture conditions integrated over the last several months. While both the PDSI and PHDI indices show long-term moisture conditions, the PDSI depicts meteorological drought while the PHDI depicts hydrological drought. The PDSI map may show less severe and extensive drought (as well as wet spell conditions) in some parts of the country than the PHDI map because the meteorological conditions that produce drought and wet spell conditions are not as long-lasting as the hydrological impacts.
Used together, the Palmer Z Index and PHDI maps show that short-term drought occurred across much of the West and parts of the central and southern Plains and Southeast, expanding and intensifying long-term dry conditions in the West and contracting long-term wet conditions in parts of the central Plains and coastal Southeast (PHDI maps for October compared to September). Short-term wet conditions in Montana, the Great Lakes, Ohio Valley, and Southeast expanded or intensified long-term wet conditions in those regions. Short-term wet conditions in parts of the Northeast contracted long-term dry conditions.
Standardized Precipitation Index
The Standardized Precipitation Index (SPI) measures moisture supply. The SPI maps here show the spatial extent of anomalously wet and dry areas at time scales ranging from 1 month to 24 months.
The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years. Dry conditions are evident across large parts of the West at the 1- to 12-month time scales. Parts of the Pacific Northwest and southern to central Rockies are dry at 24 months. Parts of the central to northern Plains are dry at 1-12 months. The southern High Plains (west Texas) to central High Plains (eastern Colorado and eastern Wyoming) are dry at the 2 to 24-month time scales. Southern Texas is dry at the 1-, 3-, and 24-month time scales. The Mid-Mississippi Valley (Iowa to Illinois) is dry at 1 and 3 months, with dryness persisting into the 1- to 12-month time scales in western Iowa and eastern Nebraska. Parts of the southern Great Lakes are dry at 2 and 6-12 months. Much of the Northeast is dry at 6 months and parts are dry at 2 to 12 months. Most of the country east of the Rockies is wet at 24 months; wet conditions dominate the Great Lakes and Lower Mississippi Valley to Gulf of Mexico and Mid-Atlantic coasts at 1 to 12 months.
Standardized Precipitation Evapotranspiration Index
The SPI measures water supply (precipitation), while the SPEI (Standardized Precipitation Evapotranspiration Index) measures the combination of water supply (precipitation) and water demand (evapotranspiration as computed from temperature). Warmer temperatures tend to increase evapotranspiration, which generally makes droughts more intense.
October 2020 continued a trend of very warm temperatures across the West, with record heat occurring in California and parts of the Four Corners States. The October heat, combined with record heat from the spring through summer, gave several states a record hot October, August-October, May-October, and January-October. California had a record warm October. States having a record warm August-October include California, Nevada, Utah, Oregon, and Arizona. States having a record warm May-October include California, New Mexico, and Arizona. In the West, New Mexico and Arizona had the warmest January-October. Precipitation for October, August-October, May-October, and January-October was below normal to record dry in these areas. The combination of hot and dry conditions resulted in a much more severe SPEI than SPI in the West for October, August-October (SPEI vs. SPI), May-October (SPEI vs. SPI), and January-October (SPEI vs. SPI).
Several states in the West had the driest SPI and driest SPEI for several time periods, although the magnitude of the SPEI was more extreme than the magnitude of the SPI. The following states are among those whose SPI was not the driest on record but the SPEI was the driest for the time period. Colorado had the driest SPEI on record for August-October and the third driest SPI. California had the driest SPEI on record for May-October and the second driest SPI. The SPEI for New Mexico was driest on record for August-October, June-October, May-October, and April-October, while the SPI was not driest on record for those time periods. Arizona had the driest SPEI on record for January-October and the fourth driest SPI for that time period. Arizona's SPEI was driest on record for all time periods from December-October through September-October while the SPI was not driest on record for September-October, March-October, February-October, January-October, and December-October. But Arizona's SPI was the driest on record for the other time periods — April-October through August-October — meaning these time periods had both the driest SPEI and driest SPI.
Regionally, the West had the warmest and second driest August-October, second warmest and second driest May-October, and fifth warmest and sixth driest November-October. The driest May-October occurred in 2002, driest August-October in 1952, and driest November-October in 1976-77. November-October temperatures across the West have shown a significant warming trend since the 1980s. Overall precipitation for November-October shows large multi-year swings from wet to dry, but no significant long-term trend. The increasing temperature trend, however, means more evapotranspiration is occurring than before and this makes the dry spells, when they happen, result in increasingly more intense droughts.
Much of the West has experienced persistent warmer-than-normal temperatures for most of the last nine years. The unusual warmth has made the SPEI more extreme than the SPI for those dry areas in the West at the longer time scales (SPEI maps for last 12, 24, 36, 48, 60, 72 months) (SPI maps for last 12, 24, 36, 48, 60, 72 months).
Regional Discussion
Hawaii
October had a mixed precipitation anomaly pattern over Hawaii, with drier-than-normal conditions dominating over the last 2 to 7 months. A mixed anomaly pattern returned at the 9- to 24-month time scales, where dry conditions were more often found on windward sides of the islands and wetter-than-normal conditions on the lee sides. Wet conditions dominated at 36 months with a mixed anomaly pattern at longer time scales (last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months) (climate engine model percent of normal precipitation map for the last month). Below-normal monthly streamflow dominated on many islands. Drought and abnormal dryness expanded across parts of Hawaii. The statewide moderate to extreme drought area expanded from 39.7 percent by the end of Sepember to 71.8 percent by the end of October.
Alaska
October 2020 was drier than normal across much of Alaska. Dryness was especially notable in the southern sections at the 2-month time scale. At the 3- to 7-month time scales, the eastern interior sections were wetter than normal, with this region surrounded by drier-than-normal conditions along the southern, western, and northern coasts. At the 9- to 12-month time scales, drier-than-normal areas were mostly confined to the Aleutians and southern coastal regions, with dry areas shifting to the south central coast to panhandle at longer time scales. (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months) (high elevation SNOTEL station precipitation maps for last 1 and 10 months, and SNOTEL basin maps for the last 1 and 10 months) (gridded precipitation percentile maps for the last 1, 3, and 10 months) (climate division precipitation rank maps for the last 1, 3, 6, 10, 12 months) (Leaky Bucket model precipitation percentile map). October was warmer than normal across the western and northern portions of the state and cooler than normal over the panhandle. By 3 months, warmer-than-normal temperatures spread across most of Alaska with near to cooler-than-normal temperatures in the panhandle, and this pattern persisted to the last 6 months. Warmer-than-normal conditions retreated to the west coast at the 10-month time scale with cooler-than-normal temperatures extending from the panhandle to the interior portions. At 12 months, cooler-than-normal temperatures were limited to the interior to eastern sections with warmer-than-normal conditions to the north, west, and south (low elevation station temperature maps for the last 1, 2, 3, 4, 10, 12 months) (gridded temperature percentile maps for the last 1, 3, and 10 months) (climate division temperature rank maps for the last 1, 3, 6, 10, 12 months) (Leaky Bucket model temperature percentile map). The combination of warmer- and drier-than-normal October conditions contributed to a below-normal snow pack in many areas. Modeled soil moisture and satellite-based soil moisture estimates showed drier-than-normal conditions in southern coastal, western coastal, and northeastern areas, while streamflow was mostly near to above normal except in southern parts of the panhandle. Abnormal dryness continued in the northwest and south central coastal areas and moderate drought continued in the northwest. Moderate drought held onto 0.9 percent of the state with abnormal dryness and moderate drought shrinking to cover 11.1 percent of the state on the November 3rd USDM map.
Puerto Rico and U.S. Virgin Islands
October 2020 had a mixed precipitation anomaly pattern across Puerto Rico (PR) and the U.S. Virgin Islands (USVI). Drier-than-normal conditions dominated by 3 months. At the 6-month time scale, it was drier than normal over the USVI and eastern PR and wetter than normal over central to western portions of PR. Wetter-than-normal conditions dominated most of PR by the 12-month time scale while the USVI continued drier than normal. It was mostly drier than normal across the USVI and PR at the 24 and 36 months, but wetter than normal at longer time scales (radar-based precipitation anomaly estimates for the last 1, 2, 3, 6, 10, 12 months) (low elevation station precipitation maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months). (climate engine model percent of normal precipitation map for October).
Root zone analyses indicated that soil conditions continued dry along the immediate southern and northwest coasts of PR. There were some low streams in western PR but most streams were near normal. Three small patches of abnormal dryness dotted PR on the November 3rd USDM map, while the USVI were free of drought and abnormal dryness.
CONUS State Precipitation Ranks
October 2020 was drier than normal across most of the West to Great Plains and parts of the Midwest, Northeast, and Southeast. Record dryness occurred in parts of the Southwest. Twelve states in the West to Midwest had a precipitation rank in the driest third of the 126-year historical record for October, including three in the top ten driest category — California (second driest), Utah (sixth driest), and Nevada (sixth driest).
August-October was drier than normal across most of the West to Great Plains and much of the Midwest and Northeast. Record dryness occurred in parts of the West to central Plains. Twenty states in these regions had a precipitation rank in the driest third of the historical record, including eight in the top ten driest category — California, Utah, Nevada, and Arizona (each ranking driest on record); New Mexico, Colorado, and Nebraska (each ranking second driest on record); and Kansas (fifth driest).
Like the last 3 months, the last 6 months (May-October) were drier than normal across most of the West, Great Plains, and Northeast, and parts of the Midwest. Record dryness occurred in much of the Southwest. Eighteen states in these regions had a precipitation rank in the driest third of the historical record, including seven in the top ten driest category — Utah, Nevada, and Arizona (each ranking driest on record); New Mexico (second driest); Colorado (fourth driest); Wyoming (fifth driest); and California (seventh driest). In the Northeast, Connecticut ranked 12th driest and Rhode Island 14th driest.
Similarly, the year to date (January-October) was drier than normal across most of the West, Great Plains, and Northeast, and parts of the Midwest. Record dryness occurred in parts of the West. Twenty states in these regions had a precipitation rank in the driest third of the historical record, including seven in the top ten driest category — Utah (driest on record), Colorado (second driest), Nevada and New Mexico (each fourth driest), Arizona (fifth driest), California (seventh driest), and Wyoming (ninth driest). In the Northeast, Connecticut ranked 13th driest and Rhode Island 15th driest.
Like the year to date, the last 12 months (November 2019-October 2020) were drier than normal across most of the West, Great Plains, and Northeast, and parts of the Midwest and central Gulf of Mexico coast. Eighteen states in these regions had a precipitation rank in the driest third of the historical record, including four in the top ten driest category — Colorado (third driest), Nevada and Utah (each fourth driest), and Wyoming (ninth driest). Oregon ranked 11th driest, North Dakota 12th driest, and New Mexico 13th driest.
Agricultural Belts
During October 2020, the Primary Hard Red Winter Wheat agricultural belt was mostly drier and cooler than normal. The month ranked as the 38th driest and 17th coolest October, regionwide, in the 1895-2020 record.
As of November 3, drought affected approximately 45 percent of spring wheat production, 41 percent of winter wheat production, 40 percent of cattle inventory, 34 percent of corn production, 32 percent of hay acreage, and 26 percent of soybean production. These were all increases compared to the end of September.
As reported by the USDA, at the end of October (November 1), topsoil moisture was short or very short (dry or very dry) across 50 percent or more of all of the states in the West and Great Plains except Arizona, Oklahoma, and Washington, and ranged from 51 percent in Texas to 83 percent in Utah and 82 percent in Colorado. Topsoil moisture was more than 30 percent short or very short in New York (31 percent), Iowa (41 percent), Washington (48 percent), and New Hampshire (79 percent). Subsoil moisture was short or very short across 80 percent of California, 77 percent of Colorado, 65 percent of Idaho, 53 percent of Iowa, 62 percent of Kansas, 58 percent of Montana, 66 percent of Nebraska, 65 percent of Nevada, 54 percent of New Hampshire, 83 percent of New Mexico, 60 percent of North Dakota, 77 percent of Oregon, 52 percent of Pennsylvania, 100 percent of Rhode Island, 62 percent of South Dakota, 53 percent of Texas, 70 percent of Utah, and 84 percent of Wyoming. Nationwide, 45 percent of the topsoil and 44 percent of the subsoil were short or very short of moisture, and 34 percent of the cotton crop and 19 percent of the winter wheat crop were in poor to very poor condition. These national figures were the same or less than a month ago for soil moisture and more than a month ago for the cotton crop.
U.S.-Affiliated Pacific Islands
The NOAA National Weather Service (NWS) offices, the Pacific ENSO Applications Climate Center (PEAC), and partners provided reports on conditions across the Pacific Islands.
In the U.S. Affiliated Pacific Islands (USAPI) (maps — Federated States of Micronesia [FSM], Northern Mariana Islands, Marshall Islands [RMI], Republic of Palau, American Samoa, basinwide), October 2020 was drier-than-normal in the southern FSM and at Chuuk. It was near to wetter than normal at Pago Pago (American Samoa) and in the Marianas, Palau, RMI, and the rest of the FSM.
Monthly precipitation amounts were below the monthly minimum needed to meet most water needs (4 inches in the Marianas and Pago Pago, and 8 inches elsewhere) at Kapingamarangi (in southern FSM), due mostly to the ongoing La Niña. October precipitation was above the monthly minimums at the rest of the USAPI stations in Micronesia and American Samoa. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then water shortages or drought become a concern.
The tropical Pacific climatology can experience extremes in precipitation, from very low precipitation during the dry season to very high precipitation during the wet season. This can result in monthly normal precipitation values that are well above the monthly minimum needed to meet most water needs. This was the case during October 2020. The monthly precipitation was enough to end or stay out of drought, but still was below normal because the normals were so high. This was the case at Chuuk (October 2020 precipitation 10.57 inches, October monthly normal mean 11.40 inches).
Even with above-normal precipitation for October across Micronesia and for September in eastern Micronesia, most stations were drier than normal for the last 10 and 12 months.
| Station Name | Nov 2019 | Dec 2019 | Jan 2020 | Feb 2020 | Mar 2020 | Apr 2020 | May 2020 | Jun 2020 | Jul 2020 | Aug 2020 | Sep 2020 | Oct 2020 | Nov- Oct |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 87% | 177% | 81% | 37% | 64% | 65% | 116% | 98% | 65% | 95% | 167% | 92% | 94% |
| Guam NAS | 214% | 29% | 75% | 125% | 64% | 98% | 240% | 55% | 81% | 86% | 87% | 146% | 89% |
| Kapingamarangi | 229% | 67% | 83% | 52% | 127% | 125% | 33% | 43% | 40% | 36% | 9% | 15% | 63% |
| Koror | 99% | 88% | 20% | 123% | 63% | 146% | 205% | 81% | 55% | 164% | 62% | 170% | 96% |
| Kosrae | 98% | 62% | 51% | 158% | 71% | 171% | 164% | 161% | 96% | 87% | 114% | 149% | 96% |
| Kwajalein | 111% | 99% | 112% | 156% | 66% | 145% | 92% | 88% | 89% | 54% | 144% | 140% | 103% |
| Lukonor | 66% | 91% | 27% | 33% | 130% | 103% | 107% | 97% | 83% | 81% | 134% | 105% | 79% |
| Majuro | 110% | 114% | 90% | 163% | 81% | 148% | 156% | 117% | 115% | 85% | 101% | 176% | 120% |
| Pago Pago | 74% | 140% | 163% | 273% | 77% | 166% | 72% | 389% | 201% | 179% | 228% | 201% | 148% |
| Pohnpei | 168% | 132% | 57% | 85% | 69% | 125% | 125% | 79% | 62% | 98% | 120% | 121% | 103% |
| Saipan | 126% | 95% | 60% | 102% | 78% | 19% | 46% | 54% | 57% | 68% | 74% | 104% | 75% |
| Yap | 105% | 116% | 23% | 63% | 25% | 80% | 105% | 154% | 51% | 72% | 81% | 104% | 82% |
| Station Name | Nov 2019 | Dec 2019 | Jan 2020 | Feb 2020 | Mar 2020 | Apr 2020 | May 2020 | Jun 2020 | Jul 2020 | Aug 2020 | Sep 2020 | Oct 2020 | Nov- Oct |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 9.26" | 19.91" | 8.20" | 2.69" | 5.29" | 8.13" | 13.09" | 11.45" | 7.77" | 12.20" | 19.61" | 10.57" | 128.17" |
| Guam NAS | 15.76" | 1.46" | 2.99" | 3.79" | 1.33" | 2.47" | 8.16" | 3.40" | 8.26" | 12.68" | 10.96" | 16.75" | 88.01" |
| Kapingamarangi | 21.27" | 6.55" | 7.60" | 4.84" | 14.52" | 17.06" | 3.93" | 5.87" | 5.59" | 2.94" | 0.86" | 1.19" | 92.22" |
| Koror | 11.29" | 9.86" | 2.02" | 10.50" | 4.66" | 10.70" | 24.24" | 14.21" | 10.13" | 22.13" | 7.28" | 20.11" | 147.13" |
| Kosrae | 13.55" | 10.06" | 8.50" | 20.45" | 11.33" | 29.87" | 29.07" | 23.64" | 14.26" | 12.41" | 16.16" | 16.25" | 205.55" |
| Kwajalein | 12.52" | 6.62" | 3.53" | 4.12" | 1.54" | 7.64" | 6.15" | 6.09" | 8.82" | 5.24" | 15.51" | 15.64" | 93.42" |
| Lukonor | 6.01" | 10.23" | 2.26" | 2.93" | 12.06" | 11.63" | 12.52" | 11.34" | 13.18" | 11.35" | 13.63" | 11.83" | 118.97" |
| Majuro | 14.83" | 13.03" | 6.93" | 11.19" | 5.32" | 13.95" | 15.78" | 12.83" | 12.85" | 9.97" | 11.25" | 22.35" | 150.28" |
| Pago Pago | 7.48" | 17.93" | 21.77" | 32.73" | 8.19" | 15.56" | 6.96" | 20.76" | 11.17" | 9.63" | 14.90" | 18.63" | 185.71" |
| Pohnpei | 24.91" | 21.17" | 7.52" | 8.16" | 9.05" | 23.03" | 24.91" | 11.70" | 9.53" | 13.99" | 15.02" | 18.49" | 187.48" |
| Saipan | 7.06" | 3.64" | 1.53" | 2.63" | 1.47" | 0.50" | 1.10" | 1.96" | 5.11" | 8.88" | 7.46" | 11.08" | 52.42" |
| Yap | 9.30" | 9.89" | 1.46" | 3.28" | 1.14" | 4.50" | 8.22" | 18.56" | 7.71" | 10.61" | 10.98" | 12.71" | 98.36" |
| Station Name | Nov 2019 | Dec 2019 | Jan 2020 | Feb 2020 | Mar 2020 | Apr 2020 | May 2020 | Jun 2020 | Jul 2020 | Aug 2020 | Sep 2020 | Oct 2020 | Nov- Oct |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 10.61" | 11.25" | 10.10" | 7.25" | 8.32" | 12.47" | 11.30" | 11.66" | 11.98" | 12.86" | 11.71" | 11.51" | 136.77" |
| Guam NAS | 7.38" | 5.11" | 4.01" | 3.03" | 2.07" | 2.53" | 3.40" | 6.18" | 10.14" | 14.74" | 12.66" | 11.44" | 99.09" |
| Kapingamarangi | 9.27" | 9.84" | 9.15" | 9.27" | 11.43" | 13.64" | 12.08" | 13.78" | 14.15" | 8.13" | 9.93" | 8.19" | 145.85" |
| Koror | 11.39" | 11.16" | 10.18" | 8.56" | 7.44" | 7.32" | 11.83" | 17.48" | 18.53" | 13.50" | 11.77" | 11.84" | 152.90" |
| Kosrae | 13.83" | 16.11" | 16.67" | 12.93" | 16.06" | 17.51" | 17.75" | 14.64" | 14.91" | 14.22" | 14.22" | 10.94" | 213.87" |
| Kwajalein | 11.28" | 6.66" | 3.16" | 2.64" | 2.35" | 5.26" | 6.72" | 6.93" | 9.87" | 9.74" | 10.74" | 11.18" | 90.41" |
| Lukonor | 9.08" | 11.27" | 8.41" | 8.93" | 9.26" | 11.31" | 11.69" | 11.65" | 15.93" | 14.04" | 10.15" | 11.32" | 151.36" |
| Majuro | 13.44" | 11.39" | 7.74" | 6.88" | 6.58" | 9.42" | 10.11" | 11.01" | 11.17" | 11.69" | 11.17" | 12.73" | 125.25" |
| Pago Pago | 10.14" | 12.84" | 13.34" | 12.00" | 10.68" | 9.39" | 9.66" | 5.33" | 5.55" | 5.38" | 6.53" | 9.26" | 125.57" |
| Pohnpei | 14.83" | 16.08" | 13.18" | 9.55" | 13.17" | 18.41" | 19.96" | 14.81" | 15.43" | 14.26" | 12.55" | 15.27" | 182.36" |
| Saipan | 5.61" | 3.85" | 2.53" | 2.59" | 1.89" | 2.63" | 2.38" | 3.62" | 8.91" | 13.13" | 10.09" | 10.62" | 70.25" |
| Yap | 8.83" | 8.51" | 6.39" | 5.19" | 4.56" | 5.63" | 7.85" | 12.04" | 15.08" | 14.82" | 13.50" | 12.18" | 120.31" |
As measured by percent of normal precipitation, Kapingamarangi was drier than normal in the short term (October and the last 3 months [August-October 2020]) and long term (year to date [January-October] and last 12 months [ November 2019-October 2020]). Guam, Saipan, and Yap were drier than normal in the long-term and for the last 3 months, but near to wetter than normal for October. Chuuk was drier than normal in the long-term and for October, but wetter than normal at the 3-month time scale. Koror and Lukonor were near to drier than normal in the long-term but near to wetter than normal in the short-term. Kosrae, Kwajalein, and Pohnpei were drier than normal for one time period and near to wetter than normal for the other three time periods. Majuro and Pago Pago were wetter than normal for all four time periods.
Based on percent of normal average (instead of normal median values), in the Marianas Islands, precipitation during October, September-October, and August-October was generally wetter than normal at southern stations and drier than normal at northern stations (Saipan). It continued drier than normal in the north with a mixed precipitation anomaly pattern in the south at the 4- to 10-month time scales. Drier-than-normal conditions dominated at longer time scales (percent of normal precipitation maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months). In the Marshall Islands, wetter-than-normal conditions dominated at the 1- to 4-month time scales, with some western stations drier than normal at 6 to 36 months and at 60 months. Those stations with enough data were wetter than normal at 48 months (percent of normal precipitation maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months).
According to the October 31st USDM produced for the USAPI, drought ended in the Marshalls but worsened in the southern FSM. Abnormally dry (D0) conditions ended at Jaluit and severe drought (D2) ended at Wotje. Kapingamarangi (southern FSM) worsened from extreme drought (D3) to exceptional drought (D4). The rest of the stations in Micronesia, and Tutuila in American Samoa, were free of drought and abnormal dryness. Storage in the Majuro reservoir briefly dipped below the 80 percent of maximum threshold for concern on the 3rd to 4th, but was above that threshold for the rest of the month, ending October at about 30.9 million gallons, which is 86 percent of maximum and above the 80 percent threshold for concern. The National Weather Service office in Guam issued three Drought Information Statements for the drought in October (on October 2, 16, and 30) discussing the conditions in the USAPI. Severe drought impacts continued during October in the southern FSM. Observers in Kapingamarangi reported that five of the six primary water tanks were empty as of October 27, and vegetation was mostly brown with no banana or breadfruit left. A relief ship (the Federated States Ship [FSS], "Independence") brought 730 gallons of potable water early in October and another trip to bring more water and food supplies was occurring as the month ended.
The last one to 12 months have been especially dry at some of the islands in Micronesia (based on monthly and seasonal precipitation ranks) and the last 4 to 12 months have been dry at others. October 2020 was the fifth driest October in a 31-year record at Kapingamarangi. The six time periods from December-October through May-October were the driest on record at the station, September-October was the third driest, and the remaining time periods were second driest. Saipan had the second or third driest November-October through June-October, and fourth driest July-October and August-October. Lukonor had the sixth or seventh driest November-October to January-October. Nukuoro ranked sixth driest for July-October (out of 37 years of data). Pingelap ranked sixth driest for August-October (36 years). Ulithi had the second driest July-October (36 years) and third driest August-October, June-October, and March-October. Yap ranked fourth driest in a 70-year record for July-October. Jaluit had the fourth driest June-October (36 years).
The following analysis of historical data for the USAPI stations in the Global Historical Climatology Network-Daily (GHCN-D) dataset, augmented with fill-in data from the 1981-2010 Normals, helps put the current data into historical perspective by computing ranks based on the period of record. The table below lists the precipitation ranks for October 2020, May-October 2020 (last 6 months), and November 2019-October 2020 (the last 12 months). Some stations have a long period of record and their dataset is fairly complete, while other stations have a shorter period of record and the dataset has some missing data.
| Station | October 2020 | May-Oct 2020 | Nov 2019-Oct 2020 | Period of Record | |||
|---|---|---|---|---|---|---|---|
| Rank | Years | Rank | Years | Rank | Years | ||
| Ailinglapalap | 37 | 37 | 35 | 36 | 29 | 34 | 1981-2020 |
| Chuuk | 24 | 70 | 26 | 69 | 17 | 69 | 1951-2020 |
| Fananu | 7 | 7 | -- | 3 | -- | 2 | 2003-2020 |
| Guam | 53 | 64 | 19 | 64 | 18 | 63 | 1957-2020 |
| Jaluit | 24 | 37 | 6 | 36 | 10 | 34 | 1981-2020 |
| Kapingamarangi | 5 | 31 | 1 | 20 | 2 | 19 | 1962-2020 |
| Koror | 69 | 70 | 55 | 68 | 34 | 68 | 1951-2020 |
| Kosrae | 44 | 52 | 35 | 41 | 20 | 34 | 1954-2020 |
| Kwajalein | 57 | 69 | 34 | 69 | 29 | 68 | 1952-2020 |
| Lukonor | 21 | 36 | 12 | 24 | 6 | 24 | 1981-2020 |
| Majuro | 65 | 67 | 56 | 66 | 54 | 66 | 1954-2020 |
| Mili | 33 | 37 | 33 | 35 | 33 | 33 | 1981-2020 |
| Nukuoro | 35 | 38 | 10 | 36 | 13 | 35 | 1981-2020 |
| Pago Pago | 50 | 55 | 54 | 55 | 54 | 54 | 1966-2020 |
| Pingelap | 29 | 37 | 16 | 35 | -- | 32 | 1981-2020 |
| Pohnpei | 53 | 70 | 21 | 69 | 36 | 69 | 1951-2020 |
| Saipan | 23 | 40 | 2 | 40 | 2 | 31 | 1981-2020 |
| Ulithi | 24 | 37 | 9 | 36 | -- | 32 | 1981-2020 |
| Utirik | -- | 18 | -- | 6 | -- | 2 | 1985-2020 |
| Woleai | 20 | 36 | 12 | 27 | 8 | 26 | 1968-2020 |
| Wotje | 36 | 37 | 30 | 36 | 30 | 33 | 1981-2020 |
| Yap | 37 | 70 | 19 | 69 | 9 | 69 | 1951-2020 |
SPI values for seven time periods for Pacific Islands, computed by the Honolulu NWS office.
NOAA Regional Climate Centers
More information, provided by the NOAA Regional Climate Centers and others, can be found below.
Southeast
As noted by the Southeast Regional Climate Center, temperatures were above average across much of the Southeast region and Puerto Rico for the month of October, and precipitation was variable with a few wet and dry extremes recorded. The driest locations were found across eastern Georgia, central South Carolina, eastern North Carolina, and the Panhandle of Florida. Most of Puerto Rico and the US Virgin Islands received normal amounts of precipitation for the month.
The entire Southeast region and Puerto Rico remained drought-free for the month of October. At the beginning of the month, small pockets of abnormally dry conditions (D0) were found in Georgia, Alabama, and southern Puerto Rico. By the end of the month these pockets of dryness (D0) expanded slightly in Georgia, South Carolina, and southern Puerto Rico. Growers had to irrigate the groves, as modest amounts of precipitation fell in the citrus growing region of Florida. Abnormally dry conditions expanded slightly in the Midlands and Lowcountry of South Carolina and although the young strawberry crop looked good, there were some reports of spider mites. Overall, however, vegetables were growing well.
South
As explained by the Southern Regional Climate Center, temperatures and precipitation for the month of October varied spatially across the Southern region. Temperatures were cooler than normal in the north and west and warmer than normal in the south and east. Parts of central and southwestern Arkansas, southeastern and northwestern Louisiana, southern and western Oklahoma, and northern, central, eastern, western, and southern Texas received 50 percent or less of normal precipitation. Parts of southwestern Arkansas as well as eastern, central, western, and southern Texas received 25 percent or less of normal precipitation, while parts of western and southern Texas received 2 percent or less of normal precipitation. In contrast, parts of northwestern Oklahoma, northern Texas, central and southwestern Louisiana, northwestern and eastern Arkansas, southeastern Mississippi, and central and eastern Tennessee received 150 percent or more of normal precipitation, while parts of northwestern Arkansas, north-central Louisiana, and western Tennessee received precipitation 200 percent or more of normal.
At the end of October, drought conditions mainly deteriorated across the Southern region. Exceptional drought conditions expanded and persisted across western and northwestern Texas. Extreme drought conditions persisted across parts of Oklahoma and Texas, with new areas developing or expanding across southwestern and western Oklahoma as well as northern, western, and southwestern Texas. Severe drought classifications expanded across western Oklahoma as well as northern, western, southern, and central Texas. Moderate drought classifications expanded or developed across northern and western Oklahoma as well as northern, western, central, southern, and eastern Texas, while moderate drought conditions persisted across northwestern Arkansas. There was an increase in the overall area experiencing abnormally dry conditions, with conditions developing or expanding across northeastern, northern, central, and western Oklahoma; northern, southern, eastern, and central Texas; southeastern and northwestern Louisiana; and northwestern Arkansas. There was slight improvement across northwestern and southeastern Mississippi, as abnormally dry conditions contracted or were eliminated.
Midwest
As described by the Midwest Regional Climate Center, October temperatures were well below normal in the northwestern Midwest and near normal in the southeastern Midwest. Regionwide temperatures were 47.9 degrees F (8.8 C) which was 3.1 degrees F (1.7 C) below normal. October precipitation ranged widely across the Midwest leaving the regionwide total near normal. The regional total was 3.13 inches (80 mm) which was just 0.12 inch (3 mm) above normal. Values ranged from less than 25 percent of normal to more than 200 percent of normal.
Drought in the Midwest peaked mid-month with nearly 17 percent of the region in drought before dropping off to under 12 percent later in the month. The area of the region in severe drought remained around 4 to 5 percent and the area in extreme drought remained around 0.5 to 1.0 percent of the region in October. The areas of extreme drought were located in northwestern Iowa and southwestern Missouri. Severe drought was primarily in Iowa and Missouri, but also extended into small parts of southwestern Minnesota and central Illinois as well during October.
Northeast
As explained by the Northeast Regional Climate Center, during October, the Northeast received 4.33 inches (109.98 mm) of precipitation, 112 percent of normal, and the region's average monthly temperature was 51.1 degrees F (10.6 degrees C), 1.7 degrees F (0.9 degrees C) warmer than normal.
The USDM released on October 1 showed 45 percent of the Northeast in an extreme, severe, or moderate drought and 25 percent as abnormally dry. During the month, beneficial rainfall improved drought conditions in portions of New England, most notably in northern and western Maine; however, drought and abnormal dryness expanded or intensified in New York, Pennsylvania, northern West Virginia, and western Maryland. The USDM released on October 29 showed 47 percent of the Northeast in an extreme, severe, or moderate drought and 24 percent as abnormally dry.
There were numerous impacts from the drought and abnormally dry conditions. During October, streamflow and groundwater levels continued to be below normal in many of the drought areas, with some sites setting daily record low streamflows. Lower than usual streamflow on the Hudson River in New York led to increased sodium levels in Poughkeepsie's water supply. Some lake levels in New Hampshire were the lowest they had been in decades. Water restrictions were enacted or remained in place for numerous locations in Massachusetts and several locations in Connecticut, Maine, New York, and Pennsylvania. As of October 28, 167 community water systems, eight municipalities, and some private well users in New Hampshire had restrictions in place. In addition, dry wells were reported in New England. Assistance was available for low-income residents in New Hampshire that use private wells and were experiencing little or no water because of the drought. Aquarion Water Company issued a mandatory ban on automatic irrigation systems and sprinklers and revoked irrigation variances for customers in southwest Fairfield County, Connecticut, which hit its third drought trigger. Worcester, Massachusetts, took one of its reservoirs offline due to drought-related low water levels. With drought conditions and an old, leaky water system, the Emerald Lake Village District in Hillsborough, New Hampshire, had spent more than 110,000 dollars to haul in water. A lower-than-usual water table has helped construction along the waterfront in Bangor, Maine, to move ahead of schedule.
Agriculture continued to suffer. In late October, potato yields were expected to be down by more than 20 percent in northern Maine. One Massachusetts farmer reported drought-related expenses of more than 50,000 dollars. Some cranberry growers in Massachusetts reported losses due to a lack of water from drought conditions. Christmas trees in Massachusetts were affected by the drought, with one farm losing around a third of its saplings. With reduced yields, a farm in Vermont had to buy hay for its cows at a cost of 15,000 to 20,000 dollars. Drought conditions in Connecticut slowed maple syrup production, with one producer expected to lose around 60,000 dollars in revenue. Portions of New England were designated as natural disaster areas by the U.S. Department of Agriculture, making some farmers eligible for federal assistance. Fall foliage peaked earlier than usual in portions of northern New England and New York, while drought-stressed trees in southern New England dropped leaves prematurely. This year's drought could affect next year's foliage display in the region and reduce next year's growth of red oak and white pine trees in New Hampshire. Fire risk remained elevated in areas of New England, New York, and Pennsylvania that were experiencing drought and abnormal dryness. In Massachusetts, there were 52 fires in a nine-day period from late September to early October. The state's fire tower network was extended due to the increased fire risk. Low water levels were reported in fire suppression ponds in eastern Connecticut. After beneficial rain in mid-October, New Hampshire lifted its fire ban for public woodlands.
High Plains
As summarized by the High Plains Regional Climate Center, it was a dry month for the High Plains overall, with below-normal temperatures prevailing throughout a large part of the region. Precipitation was less than 50 percent of normal across much of North Dakota, Nebraska, Wyoming, Colorado, eastern South Dakota, and northern Kansas. Some locations received very little precipitation, which placed this October among the top 10 driest Octobers on record.
Much of the region experienced an intensification of drought conditions. Perhaps the most notable impact of drought this month was the continuation of wildfires raging across Colorado and, to a lesser extent, Wyoming. Snowfall and cooler temperatures toward the end of the month helped ease fire conditions. One benefit of the dryness was that producers were able to get out in the fields and harvest their crops. As of the end of October, all High Plains states were ahead of the 5-year average for both corn and soybean harvest. In fact, Nebraska and North Dakota had completed soybean harvest by the end of the month. Despite drought conditions, corn and soybeans fared pretty well throughout the region. North Dakota and South Dakota are expected to have record corn yields this year. However, drought conditions have caused winter wheat to struggle. More than 20 percent of the winter wheat crop was rated poor or very poor in Colorado, Kansas, and Nebraska, and more moisture is needed to ensure sufficient growth.
Dry conditions in October led to continued development and intensification of drought throughout the High Plains. According to the USDM, the area experiencing drought (D1-D4) increased from approximately 62 percent to 71 percent over the course of the month. By the end of October, over 98 percent of the region was experiencing drought or abnormal dryness (D0-D4). Exceptional drought (D4) increased in areal coverage across Colorado, expanding into northwestern, southwestern, and central parts of the state. Extreme drought (D3) spread into eastern Colorado and further expanded in Wyoming and the Nebraska Panhandle, reaching into southwestern South Dakota and western Kansas. D3 developed in southeastern South Dakota as well. Severe drought (D2) expanded across western and central North Dakota, western Wyoming, southern and eastern areas of Nebraska, and northwestern Kansas. Moderate drought (D1) developed in portions of central and eastern Kansas, while abnormally dry conditions (D0) developed across the rest of the state. Only minor improvements in drought conditions occurred in October. D3 was removed from eastern Nebraska and slightly reduced in southern Colorado and northern Wyoming. Meanwhile, D1 was reduced in northeastern and west-central South Dakota. Localized precipitation in mid-October brought relief to eastern Nebraska, while other areas were fortunate to receive enough precipitation from the late-October winter storm to improve conditions.
West
As described by the Western Regional Climate Center, in summary, after a quiet start to the month, an active weather pattern developed in the Pacific Northwest into the northern Rockies beginning around October 10th and persisting through the rest of the month bringing below-normal temperatures and above-normal precipitation. Tranquil weather persisted through the entire month beneath a ridge of high pressure over California, Nevada, Arizona, and Utah leading to well above normal temperatures and below normal precipitation. California saw its warmest October on record and fourth driest which allowed several large, active wildfires to continue burning and produced ongoing degraded air quality from wildfire smoke.
While southern coastal California remains drought free, drought persists across the rest of Oregon, California, Nevada, Utah, and Arizona with large areas of extreme and exceptional drought according to the USDM at the end of October. Utah had the most widespread drought with 59% of the state in extreme drought and 29% in exceptional drought. In northern California, the states two largest reservoirs, Lake Shasta and Lake Oroville, are now at 78% and 71% of normal, respectively, mostly due to exceptionally dry conditions over the past year.
Drought continued to develop and intensify across Hawaii with one or two category degradations on several islands. The eastern side of the Big Island saw below normal precipitation and a large area of drought expansion in October. Extreme drought is now present on the Big Island, Maui, and Molokai. Hilo logged 4.82 in (122.4 mm) of precipitation, 49% of normal, making it the tenth driest October since records began in 1949. Kahului, Maui recorded 0.26 in (6.6 mm) of precipitation, 22% of normal for the month.
In Alaska, temperatures were generally above normal except for the panhandle where temperatures were 1-3 deg F below normal. Precipitation in Alaska was a mixed bag for the month. A small cluster of stations to the southeast of Fairbanks saw the greatest wet departures at 150%-300% of normal while the southern panhandle and southwest Alaska out into the Aleutians saw below normal precipitation. Dutch Harbor, on the west end of the Aleutian chain, recorded 3.4 in (86.4 mm) of precipitation, 48% of normal. Moderate drought persisted in the Northwest Arctic Borough; this is only the second time the Borough has experienced moderate drought in the USDM since 2000.