This analysis is based on preliminary data available from the Storm Prediction Center. Final tornado counts published by the Storm Prediction Center and NCEI's Storm Events Database might differ from this report. For a more detailed climatology, please visit our tornado climatology page.

According to data from NOAA's Storm Prediction Center, during August, there were 161 preliminary tornado reports. This is well above, nearly double, the 1991-2010 average of 83 tornadoes for the month of August. The majority of the U.S. August tornadoes occurred across several days and were focused in Minnesota, Illinois and up the East Coast from North Carolina to New Jersey.

The most prolific tornado-producing days were August 3-4 in which 52 tornadoes developed across North Carolina, Virginia, Maryland, Delaware and New Jersey due to Tropical Storm Isaias. Many of these were weaker tornadoes (EF-0 and EF-1) that produced light damage to agriculture, structures and residences. However, there were several EF-2 tornadoes and one EF-3 tornado across coastal North Carolina and Virginia due to Isaias. The single EF-3 tornado that occurred in coastal North Carolina was responsible for two tornado fatalities.

A second notable event for the month was August 10, in which a destructive Midwestern derecho produced at least 16 tornadoes across eastern Illinois and the Chicago metroplex. These weaker (EF-0 and EF-1) tornadoes did not produce any fatalities, but did cause scattered damage to homes and businesses.

Another notable tornado day occurred on August 14 in which 31 tornadoes were reported, primarily across central Minnesota. These were also relatively weak tornadoes (EF-0 and EF-1) that produced sporadic damage to trees, outbuildings and residences. There were also no fatalities reported.

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:

Citing This Report

NOAA National Centers for Environmental Information, Monthly Tornadoes Report for August 2020, published online September 2020, retrieved on December 7, 2023 from