According to data from NOAA's Storm Prediction Center, during May, there were 210 preliminary tornado reports. This was 76 percent of the 1991-2010 average of 276 tornadoes for the month of May. Tornadoes were reported on 27 of the 31 days during the month. Many of the days reported single digit tornado counts. Only five days during May had 10 or more reported tornadoes.
The first notable tornado days were May 4, 5 and 6, as a combined 32 preliminary tornadoes were reported. These tornadoes were scattered across Texas, Oklahoma, Mississippi, Arkansas, Alabama, Florida, North Carolina, Virginia and Kentucky. During this three-day period many of these tornadoes were rated as either EF-1 or EF-0, but there were also four EF-2 tornadoes, and one EF-3 tornado. The EF-3 occurred near Lockette, Texas on May 4 causing damage to homes, businesses, vehicles and other infrastructure. There were several injuries reported but no fatalities.
The most prolific tornado outbreak of the month was on May 11 and 12 that produced a combined 40 preliminary tornadoes. These tornadoes occurred across eastern South Dakota and southern Minnesota. During this two-day period many of these tornadoes were rated as either EF-1 or EF-0, but there were also five EF-2 tornadoes. These tornadoes produced damage to numerous homes, businesses, farms, outbuildings and other infrastructure. There were several injuries reported but no fatalities.
Another day with a high concentration of tornadoes was May 30, as 27 tornadoes impacted eastern South Dakota and west-central Minnesota. During this day many of these tornadoes were rated as either EF-1 or EF-0, but there were also four EF-2 tornadoes and one EF-3 tornado. The EF-3 tornado occurred near Altamont, South Dakota causing heavy damage to farms, outbuildings and transmission towers. Several other EF-2 tornadoes produced scattered damage across western Minnesota. This damage was more severe in Nelson and Deer River, Minnesota where homes, businesses and a baseball field were damaged. There were no reported injuries or fatalities.
Did You Know?
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:
- 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.