In the atmosphere, 500-millibar height pressure anomalies correlate well with temperatures at the Earth's surface. The average position of the upper-level ridges of high pressure and troughs of low pressure—depicted by positive and negative 500-millibar height anomalies on the September 2021 map, is generally reflected by areas of positive and negative temperature anomalies at the surface, respectively.
Monthly Temperature: September 2021
Temperature anomalies and percentiles are shown on the gridded maps below. The anomaly map on the left is a product of a merged land surface temperature (Global Historical Climatology Network, GHCN) and sea surface temperature (ERSST version 5) anomaly analysis. Temperature anomalies for land and ocean are analyzed separately and then merged to form the global analysis. For more information, please visit NCEI's Global Surface Temperature Anomalies page. The percentile map on the right provides additional information by placing the temperature anomaly observed for a specific place and time period into historical perspective, showing how the most current month, season or year compares with the past.
The global surface temperature for September 2021 was 0.90°C (1.62°F) above the 20th century average of 15.0°C (59.0°F) and was the fifth highest September temperature in the 142-year record. Only Septembers of 2015, 2016, 2019, and 2020 had a higher September temperature departure. The eight warmest Septembers have all occurred since 2014. September 2021 also marked the 45th consecutive September and the 441st consecutive month with temperatures, at least nominally, above the 20th-century average.
During the month, temperature departures of +2.0°C (+3.6°F) or higher were observed across parts of the North Pacific Ocean, central and eastern North America, southern South America, northern Africa, northern and southern parts of Asia, as well as parts of Antarctica. According to the National Snow and Ice Data Center (NSIDC), September temperatures across much of the Arctic were also above average, with some locations having temperature departures as high as +4.0°C (+7.0°F). Record-warm September temperatures were present across parts of Africa, the Atlantic Ocean, the British Isles, southern Asia, South America, and the Pacific Ocean. This encompassed about 6.43% of the world's surface with a record warm September temperature, the fourth highest September percentage since records began in 1951. Meanwhile, near- to cooler-than-average September temperatures were observed across parts of the central tropical and eastern Pacific Ocean, Alaska, Greenland, Scandinavia, and western and eastern parts of Russia. However, no land or ocean areas had record-cold September temperatures.
The Southern Hemisphere's September 2021 surface temperature departure of +0.70°C (+1.26°F) was the warmest September in the 142-year record, surpassing the previous record set in 2018 by 0.02°C (0.04°F). This was mainly driven by the very warm Southern Hempisphere land, which had its second warmest September on record. Only September 2020 was warmer. Meanwhile, the Northern Hemisphere had its fifth-warmest September on record at +1.09°C (+1.96°F).
According to NCEI's continental analysis, Africa had its warmest September on record at 1.50°C (2.70°F) above average, surpassing the previous record set in 2017 by 0.07°C (0.13°F). Nine of Africa's 10 warmest Septembers have occurred since 2002. September 1997 ranks among the 10 warmest Septembers on record.
September 2021 was also South America's warmest September on record at +1.94°C (+3.49°F). This value exceeded the previous record set in 2015 by 0.23°C (0.41°F). Nine of South America's 10 warmest Septembers have occurred since 2011. According to Argentina's Servicio Nacional Meteorológico, Argentina had its second warmest September since national records began in 1961. Minimum temperatures were above average during the month, with several locations setting new high minimum temperatures on record.
North America's September 2021 temperature departure of +1.58°C (2.84°F) was the third highest for North America on record, behind Septembers of 1998 and 2019. The contiguous U.S. had its fifth warmest September on record.
Asia also had an above-average September and ranked as the ninth-warmest September on record. The Kingdom of Bahrain had its sixth warmest September since national records began in 1902, with a temperature departure of +0.7°C (1.3°F). Hong Kong had its warmest September on record, with a mean temperature departure of +2.0°C (+3.6°F). According to the Hong Kong Observatory, Hong Kong had a total of 15 very hot days and 11 hot nights — the highest number of hot days and nights on record in September.
Although Europe had an above-average temperature, this was its coolest September since 2013. Several European countries had their top 10 warmest September on record. The United Kingdom had its second-warmest September since national records began in 1884 at 2.1°C (3.8°F) above the 1981–2010 average. Regionally, England, Wales, Scotland, and Northern Ireland had a top three warm September on record. Ireland also had an above-average September temperature, with several locations across the country having their warmest September on record.
The Netherlands had its seventh warmest September on record at 1.2°C (2.2°F) above average.
According to Meteo France, maximum (daytime) temperatures rose to 33.4°C (92.1°F) on September 13 — the highest maximum temperature for France in September since records began 1947.
Oceania also had an above-average September temperature. However, it was the coolest since 2018. During September 2021, Australia had above-average temperatures, resulting in a national mean temperature of 1.01°C (1.82°F) above the 1961–1990 average. This was the 24th warmest September in the nation's 112-year record.
(out of 142 years)
|Land||+1.39 ± 0.29||+2.50 ± 0.52||Warmest||2nd||2020||+1.47||+2.65|
|Ocean||+0.72 ± 0.14||+1.30 ± 0.25||Warmest||6th||2015||+0.83||+1.49|
|Coolest||137th||1903, 1904, 1908||-0.47||-0.85|
|Land and Ocean||+0.90 ± 0.16||+1.62 ± 0.29||Warmest||5th||2015, 2016, 2019, 2020||+0.94||+1.69|
|Land||+1.35 ± 0.23||+2.43 ± 0.41||Warmest||4th||2016||+1.61||+2.90|
|Ocean||+0.94 ± 0.14||+1.69 ± 0.25||Warmest||6th||2015||+1.13||+2.03|
|Land and Ocean||+1.09 ± 0.18||+1.96 ± 0.32||Warmest||5th||2019||+1.23||+2.21|
|Land||+1.48 ± 0.16||+2.66 ± 0.29||Warmest||2nd||2020||+1.55||+2.79|
|Ocean||+0.55 ± 0.15||+0.99 ± 0.27||Warmest||5th||2016||+0.62||+1.12|
|Land and Ocean||+0.70 ± 0.16||+1.26 ± 0.29||Warmest||1st||2021||+0.70||+1.26|
The most current data can be accessed via the Global Surface Temperature Anomalies page.
Year-to-date Temperature: January–September 2021
The January–September 2021 global surface temperature was 0.83°C (1.49°F) above average — the sixth highest such period in the 142-year record. Looking ahead, the year 2021 is very likely to rank among the ten warmest years on record, with less than 2% chance to rank among the five warmest years on record, according to a statistical analysis done by NCEI scientists.
The first nine months of the year were characterized by warmer-than-average conditions across much of the globe. Temperatures were much warmer than average across parts of North, Central and South America, Africa, western Europe, southern Asia, as well as parts of the Atlantic, Indian, and northern and western Pacific oceans. Record-warm January–September temperatures were observed across parts of the Pacific Ocean, northern Africa, and southern Asia. Cooler-than-average conditions were limited to tropical central and eastern Pacific Ocean and the south-central contiguous U.S. However, no land or ocean areas had a record-cold January–September.
According to our continental analysis, North America, South America, Africa, and Asia had a top eight warm January–September on record. Of note, Africa had its third warmest year-to-date, behind 2010 (warmest) and 2016 (second warmest). Although Oceania and Europe had an above-average January–September temperature, it was their coolest such period since 2012 and 2013, respectively.
(out of 142 years)
|Land||+1.33 ± 0.18||+2.39 ± 0.32||Warmest||6th||2016||+1.67||+3.01|
|Ocean||+0.65 ± 0.18||+1.17 ± 0.32||Warmest||7th||2016||+0.83||+1.49|
|Land and Ocean||+0.83 ± 0.18||+1.49 ± 0.32||Warmest||6th||2016||+1.06||+1.91|
|Land||+1.51 ± 0.20||+2.72 ± 0.36||Warmest||4th||2016||+1.87||+3.37|
|Ocean||+0.80 ± 0.17||+1.44 ± 0.31||Warmest||6th||2020||+1.00||+1.80|
|Land and Ocean||+1.07 ± 0.18||+1.93 ± 0.32||Warmest||6th||2016, 2020||+1.31||+2.36|
|Land||+0.86 ± 0.13||+1.55 ± 0.23||Warmest||12th||2019||+1.21||+2.18|
|Ocean||+0.54 ± 0.18||+0.97 ± 0.32||Warmest||9th||2016||+0.73||+1.31|
|Land and Ocean||+0.59 ± 0.17||+1.06 ± 0.31||Warmest||9th||2016||+0.80||+1.44|
The maps shown below represent anomalies (left, using a base period of 1961–1990) and percent of normal (right, using the same base period) based on the GHCN dataset of land surface stations. As is typical, precipitation anomalies during September 2021 varied significantly around the world.
Significantly below-average precipitation occurred across from the southwestern contiguous U.S. to parts of the northern Great Plains, as well as parts of Texas to parts of the Midwest. Southeastern Brazil, southern Chile and southern Argentina, parts of central and northern Europe, southern Australia, and parts of Asia were also drier than normal. Significantly above-average precipitation occurred in the northwestern and northeastern contiguous U.S., northern Argentina, Spain, western, southern and eastern parts of Asia, and southeastern Australia.
In early September, two separate events of heavy rain fell across parts of central Mexico, causing the overflow of rivers and streams and triggering dangerous floods. According to reports, over 500 homes were damaged.
According to reports, parts of central Africa have been affected by heavy rain since the beginning of their rainy season in July. In Chad, about 250,000 people have been affected, while over 700,000 people have been affected in Sudan and South Sudan so far. The heavy rain triggered floods that damaged infrastructures, affected farming as crops were either damaged or destroyed, and was also responsible for the loss of livestock.
Typhoon Conson was an equivalent Category 1 hurricane in the Saffir-Simpson scale at its strongest intensity. Conson made landfall across central Philippines on September 6, bringing strong winds and heavy rain that prompted floods in low-lying communities. A few days later, Typhoon Chanthu, an equivalent Category 5 hurricane in the Saffir-Simpson scale, made landfall on the Batanes Islands, northern Philippines, on September 11. Chanthu was responsible for destroying infrastructures across the Batanes Islands, as well as toppling poles and trees, causing power outages. Chanthu also affected Taiwan, with torrential rains and strong storm surges of up to 7 m (23 feet).
In the North Indian Basin, Cyclone Gulab made landfall in southeastern India on September 26. Gulab brought torrential rains to parts of India, causing significant damages, such as toppling power lines, flooding roads, and damaging homes. By September 28, Gulab weakened significantly over land. However, once it reemerged in the Arabian Sea, the system strengthened once again, reaching an equivalent Category 1 hurricane intensity. Gulab made landfall on Oman on October 3, prompting dangerous floods.
Drought conditions have severely impacted central and southern Brazil this year, resulting in one of the worst droughts for the nation in centuries. According to reports, the lack of rain has resulted in water scarcity, increased fire activity, and crop losses. The rainfall deficit also impacted the energy sector since hydroelectric reservoirs are low or empty, prompting the Brazilian government to encourage its residents to consume less energy. On September 27, strong winds caused a dust storm over San Pablo, reducing visibility drastically.
Global Precipitation Climatology Project (GPCP)
The following analysis is based upon the Global Precipitation Climatology Project (GPCP) Interim Climate Data Record. It is provided courtesy of the GPCP Principal Investigator team at the University of Maryland.
The Global Precipitation Climatology Project (GPCP) monthly data set is a long-term (1979-present) analysis (Adler et al., 2018) using a combination of satellite and gauge information. An interim GPCP analysis completed within ~10 days of the end of the month allows its use in climate monitoring.
The global precipitation map for September 2021(Fig. 1, top panel) is dominated by the rainfall of the summer monsoon over East Asia and the other large-scale features of the season, but one can also detect relatively narrow swaths of precipitation in the North Pacific and North Atlantic associated with the tracks of tropical cyclones. These open ocean tracks are even more prominent in the anomaly maps (magnitude and percentage in the middle and bottom panels of Fig. 1). However, from the middle panel figure it is clear that the summer Asian monsoon, climatologically the strongest precipitation feature on the planet, was particularly intense in September, with above average rainfall over most of South Asia, China and the Maritime Continent. The strong monsoon, with imbedded tropical cyclones, produced intense rain events across the region with flooding in northeast China, Indonesia, Indochina and western India and Pakistan. Looking back over the last few months and even the last year, this above average precipitation pattern in East Asia has been a general feature.
The El Niño-Southern Oscillation (ENSO) SST conditions in the tropical central Pacific are near neutral (slightly toward the La Niña side). The overall pattern of precipitation anomalies in the deep tropics reflect the absence of this effect, although the intense rainfall over the Maritime Continent is typical of La Niña conditions.
Over Africa the usual ITCZ feature shows above average rainfall, with a large positive anomaly over eastern part of the continent, which resulted in significant flooding in Sudan and surrounding areas, in the midst of political difficulties. Australia has remained mainly dry, although the southeast portion of the country shows above average precipitation this month. The circumpolar rainband in the Southern Hemisphere at 50–60°S has above average values over most of this feature.
The rainfall maximum over northern South America shows positive anomalies across the northern Amazon forest area, although negative anomalies along the north coast as part of a negative anomaly over the Caribbean and even the surrounding regions. Over central South America the September negative anomaly feature there in September has been persistent over the past year and is connected to the ongoing drought conditions in the region.
Over North America the very general pattern of negative anomalies in the western portion and positive anomalies in the east continues in September. The drier than normal zone in the west is an extension of the larger feature in the anomaly maps across most of the subtropical Pacific, with a more intense than normal mid-latitude precipitation feature extending from Asia into the North America coastal areas. The North American monsoon weakened in September and did not provide relief this month in the southwest U.S. The Gulf of Mexico had some tropical cyclone activity that affected parts of Texas, Louisiana and even flooding in New York City at the beginning of the month.
Floods in Spain and southern France are related to positive rainfall anomalies there. Positive precipitation anomalies are evident across the northern edge of Eurasia and across parts of northern Alaska and Canada, perhaps related to generally warm temperatures at these latitudes and associated abundant moisture.
Background discussion of long-term means, variations and trends of global precipitation can be found in Adler et al. (2017).
Ocean Heat Content
Ocean Heat Content (OHC) is essential for understanding and modeling global climate since > 90% of excess heat in the Earth's system is absorbed by the ocean. Further, expansion due to increased ocean heat contributes to sea level rise. Change in OHC is calculated from the difference of observed temperature profiles from the long-term mean.
|Basin||0-700 meters | Rank (1955-2022)|
|Entire Basin||Northern Hemisphere||Southern Hemisphere|
|Source: Basin time series of heat content|
Global OHC for July–September 2021 is the highest July–September OHC in our records, which extend back to 1955. Overall, the latest quarterly OHC reveals widespread warmer than normal conditions relative to the 1955–2006 mean, a situation observed since the end of 2016. Global OHC has returned to record high levels after the relative lows observed around mid-2020, which coincides with the weakening since late 2020 of the 2020–2021 La Niña event. Higher, > 10x105 J/m3, than normal OHC conditions appear in a narrow band along the Equator in the North Pacific Ocean and also dominate most of the tropical Atlantic Ocean. Much higher, > 30x105 J/m3, than normal OHC conditions continue to exist in the Gulf Stream/North Atlantic Current, the South Atlantic Ocean, the Kuroshio Current/Kuroshio Extension/North Pacific Current, and along the Antarctic Circumpolar Current in the Indian Ocean sector. Cool conditions, < -10x105 J/m3, persist in the subtropical South Indian Ocean, in the subpolar North Atlantic Ocean south of Greenland and Iceland, and in the southern Norwegian Sea. The warm signal observed in the central and western tropical South Pacific Ocean extends now northwestward to the South China Sea. Higher, > 10x105 J/m3, than normal OHC conditions dominate most of the North Indian Ocean and the Indonesian Throughflow.
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