NOAA's National Centers for Environmental Information
Visit:NCEI U.S. Tornadoes
May 2021 Tornado Occurrences
Source: SPC
According to data from NOAA's Storm Prediction Center, during May, there were 288 preliminary tornado reports. This is near the 1991-2010 average of 276 tornadoes for the month of May. Historically, the month of May represents the peak of the U.S. tornado season, as it has the highest average number of tornadoes per month based on the 1991-2010 reference period. May was an active month for tornadoes with at least one tornado reported on 25 separate days during the month. The May tornado count escalated quickly at the beginning of the month, as at least 96 confirmed tornadoes occurred on May 2-4. However, there were no EF-3+ tornadoes reported across the CONUS during May. If this verifies, it will be the first time, since reliable records began in 1950, that no EF-3+ tornadoes occurred during the month of May. The month also had no tornado-related deaths, which is the first May without a tornado death since 2014. The days with the highest count of tornadoes and notable impacts are noted below in chronological order.
On May 2-4, there were at least 96 tornadoes that developed across several southeastern states. On May 2, there were dozens of tornadoes that formed along a southwest to northeast track through central Mississippi. These torandoes produced damage to homes, vehicles and infrastrucutre, but there were no tornado-related fatalities. May 3 and 4 produced numerous tornadoes along the Tennessee and Kentucky border and another cluster of tornadoes formed across northern Georgia into South Carolina. The strongest tornado occurred on May 3rd in Greenwood, SC and was rated an EF-2 with winds of 125 mph. Another tornado rated EF-1, with winds of 110 mph occurred in York County, SC, causing major damage at a family farm killing thousands of turkeys. There were also many isolated tornadoes in other states including Texas, Arkansas, Illinois, Pennsylvania, Maryland and Virginia. In total, this three-day event produced six EF-2, 35 EF-1 and 38 EF-0 tornadoes that collectively caused damage to homes, businesses and vehicles. There were also numerous weaker tornadoes of unknown or not-classified (EF-U) that were part of this storm system. Also, despite the larger number of tornadoes during this three-day event there were reported injuries but no tornado-related fatalities.
On May 16-19, there were 51 tornadoes that were scattered across numerous states including Colorado, Wyoming, Kansas, New Mexico, Texas, Arkansas, Louisiana, Mississippi, South Dakota and Minnesota. The majority of these tornadoes were EF-1 or EF-0 with numerous EF-U tornadoes that were clustered in Louisiana and Minnesota on May 17 and 19, respectively. These tornadoes caused mostly minor damage to homes, vegetation and infrastructure.
On May 22-24, there were 39 tornadoes that impacted Colorado, South Dakota and Kansas. These were all weaker tornadoes that occurred over rural areas, which limited their impact, causing minor damage to vegetation and infrastructure. There was one reported injury but no tornado-related fatalities.
On May 26, there were 28 tornadoes that impacted Nebraska, Kansas, Oklahoma and Texas. The majority of the tornadoes formed along a line from southwestern Nebraska into central Kansas. These were all weaker tornadoes that caused mostly minor damage to farmsteads, homes and other infrastructure.
On May 30, there were 13 tornadoes that impacted Colorado, New Mexico, Oklahoma and Texas. These were all tornadoes that occurred over rural areas, which limited their impact and are all rated as EF-U. These tornadoes did cause minor damage to vegetation and infrastructure.
Did You Know?
Tornado Count
Final monthly tornado counts are typically less than the preliminary count. This can be due to some phenomena being inaccurately reported as tornadic activity or a single tornado being reported multiple times. Tornado accounts are reported to the local National Weather Service forecast offices who are responsible for going into the field and verifying each tornado reported. This process often takes several months to complete. Once all reports have been investigated, the final count is published by the Storm Prediction Center (SPC).
The Tornado Monthly Climate Reports are written using the preliminary numbers because the final data is not available at the time of production. Historically, for every 100 preliminary tornado reports, at least 65 tornadoes are confirmed. An error bar is depicted on the tornado count graphic representing this uncertainty in the preliminary tornado count.
The following U.S. studies performed by SPC meteorologists offer deeper context and discussion regarding the frequency and distribution of tornado intensity climatologies:
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Edwards, R., H. E. Brooks, and H. Cohn, 2021: Changes in tornado climatology accompanying the Enhanced
Fujita scale. J. Appl. Meteor. Climatol., 60, 1465-1482
DOI: 10.1175/JAMC-D-21-0058.1. - Mccarthy, Daniel & Schaefer, Joseph. (2004). Tornado trends over the past thirty years. paper presented at 14th Conference on Applied Meteorology.