No severe tornadoes struck U.S. this May for first time

Not a single severe tornado touched down in the United States in May, a first on record.

While the overall number of twisters was close to normal during the month, they were exclusively of the weaker or nonsevere variety, rated EF2 or lower on the 0 to 5 Enhanced Fujita scale for tornado damage.

Severe tornadoes are considered those that reach EF3 strength or greater, corresponding to winds of 136 mph or greater.

May’s tornadoes largely missed homes and structure, yielding relatively little impact and sparing the country of any tornado fatalities for the first time during the month since 2014.

May is ordinarily the peak month of tornado season and is known for the seemingly routine barrages of twisters that spin up across the Great Plains and central U.S.

Most of the tornadoes during the past month were short-lived and weak, and classic tornado setups were less frequent than in years past. The National Weather Service Storm Prediction Center issued 25 tornado watches, the eighth fewest since 1970.

All told, 288 tornadoes developed during the month of May, only eight of which even reached EF2 strength. The rest were EF0s, EF1s or “unrated” EFUs. Tornadoes are not assigned an EF rating if there is insufficient damage evidence to rate them.

The lack of EF3 or greater ratings assigned during the month does not mean that no tornadoes of EF3 strength or greater occurred. In fact, it’s almost certain they did. However, the Enhanced Fujita scale, which is used to classify tornadoes, is a damage scale. That means that, without damage, higher-end ratings can’t be assigned.

On May 26, for instance, more than a dozen tornadoes — some likely with winds perhaps cresting in the EF3 range — swirled across extreme southern Nebraska near the Kansas border. Most were rated EFUs, since they passed over open rural landscapes with nothing to hit.