No Tornado Deaths Reported in U.S. in May or June, Historically the Two Most Active Months of the Year

For only the second time on record, the two most active months for tornadoes of May and June have passed without claiming any lives in the United States.

The only other time we escaped those two months without a tornado death was in 2005.

Halfway through the year, tornadoes have killed three people in the U.S., most recently on April 13 in Bossier Parish, Louisiana, according to NOAA's Storm Prediction Center (SPC).

Prior to that, a pair of tornadoes on Feb. 24 in Logan County, Kentucky, and Clay County, Arkansas, each resulted in one death. Those two twisters ended a record streak of 283 days without a tornado-related death in the U.S.

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At the current pace, 2018 could finish as the least-deadly year for tornadoes in official records dating to 1950. The year with the fewest number of tornado deaths in the official National Weather Service database was 1986, when 15 fatalities were reported.

In an average year, based on 30 years of data from 1987 to 2016, 69 people are killed by tornadoes in the U.S., according to the NWS.

2017 and 2016 were both well below that average, with 35 and 18 Americans, respectively, killed by twisters. In fact, the last year with an average or above-average number of tornado-related deaths was 2012, with 69 fatalities.

This year's lack of tornado deaths coincides with the least active year for twisters in more than 13 years.

A preliminary 571 tornado reports had been tallied by the NWS and SPC through June 27; an average year would have 1,004 reported tornadoes by that date.

"Accurate and timely watches and warnings – including cell phone alerts – supported in part by improved radar technology play a major role in saving lives throughout the tornado season," he told USA Today.

The biggest tornado droughts this year are in the southern Plains, or in the southern part of Tornado Alley – the area between Texas and the Dakotas that sees some of the most tornadic activity in the world.

An unfavorable jet stream position kept twisters away from Oklahoma until early May. When storm systems finally arrived, they didn't produce many tornadoes.

The jet stream did, however, produce tornadoes in the northern Rockies and High Plains, including Idaho, Wyoming and North Dakota.

The more northerly jet stream sent storm systems on a track around the U.S.-Canada border or through the Midwest for much of the spring.

That means it was far more difficult for storm systems to tap into the Gulf of Mexico moisture and southern heat. Those two ingredients, in addition to the wind shear – changing wind speed and direction with height, that the jet stream provides – are most favorable for tornadogenesis when they overlap.

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Typically, there aren't many U.S. tornado deaths after the spring severe weather season, meteorologist Harold Brooks of the National Severe Storms Laboratory told USA Today. Summer and early fall are usually quiet before the "second tornado season" from late-October through November in the Deep South, he added.

"Even a season that produces a below-average number of tornadoes can be a potentially deadly season if people are unaware of the overall risk or the impending threat of a tornado," Vaccaro also told USA Today.

Brian Donegan is a meteorologist at weather.com. Follow him on Facebook, Twitter and Instagram.