For only the second time on record, no one killed by tornadoes in US in May or June

Doyle Rice | USA TODAY

Show Caption Hide Caption Tornadoes and hail pelt Colorado Golf ball-sized hail pelted parts of Colorado on Monday, June 18, followed by multiple tornado sightings the next day.

For the first time since 2005, and only the second time on record, no one was killed by tornadoes in the U.S. in either May or June.

Those are typically two of the USA’s deadliest months for tornadoes, along with March and April. Official U.S. tornado records go back to 1950.

Although we have a long way to go, the U.S. could see its least deadly year for tornadoes on record: So far in 2018, tornadoes have killed only three people. The most recent was on April 13 in Louisiana, according to the Storm Prediction Center.

An average of 71 Americans are killed each year by tornadoes, based on data from 1987 to 2016, the Weather Channel reported.

Based on the official database, the year with the fewest tornado deaths was 1986, when 15 people died. Unofficial records – from before 1950 – show that in 1910, only 12 people were killed by tornadoes.

Not surprisingly, the lack of tornado deaths coincides with a very quiet year for twisters overall. So far, there have been 571 reports of tornadoes across the U.S. this year. (That number is preliminary and will likely be reduced once duplicate reports are discounted.)

On average, during the first six months of the year, about 1,000 tornadoes hit the U.S.

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NOAA spokesman Chris Vaccaro said the lack of tornado deaths is only partly due to fewer tornadoes: "Accurate and timely watches and warnings – including cellphone alerts – supported in part by improved radar technology play a major role in saving lives throughout the tornado season," he said.

Warm, humid air is one of the ingredients needed for tornadoes to form, and for much of the early part of the year, it was lacking in the central U.S.

Frequent rounds of chilly air from Canada, thanks to a persistent southward dip in the jet stream over the eastern U.S., helped to keep temperature and humidity surges to a minimum, according to AccuWeather.

The biggest tornado droughts this year are in the Plains states of Texas and Oklahoma, in the southern part of "Tornado Alley." An unfavorable jet stream position kept twisters away from the region until early May, the Weather Channel reported. And when storm systems finally did arrive, they didn't produce many tornadoes.

Meteorologist Harold Brooks of the National Severe Storms Laboratory said there aren't typically many U.S. tornado deaths after the spring storm season. Summer and early fall are typically quiet, he said, before the "second tornado season" of November.

Vaccaro, the NOAA spokesman, warned to not led your guard down: "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."