A recent study underscores the danger presented by nighttime tornadoes. Scientists at Northern Illinois University (NIU) found twisters that strike between midnight and dawn are two-and-a-half times more likely to result in fatalities.

National Weather Service meteorologist Jeff Johnson says nighttime tornadoes are infrequent in Iowa. “Our prime time for tornadoes is roughly 5 to 7 p.m. That’s our peak occurrence, then after dark it drops off sharply,” Johnson said. “You can get nighttime tornadoes in Iowa, but they’re much less frequent than the lower Mississippi Valley or the deep South.” The NIU scientists reported less than 32% of the tornadoes that touch down in Iowa do so between midnight and dawn.

Johnson said it’s not surprising that nighttime tornadoes are more likely to kill as most people are sleeping and unaware that a tornado warning might be in place. He advises Iowans to seek out a reliable warning system. “Probably your best bet is a well programmed NOAA Weather Radio,” Johnson said. “You can have it programmed down to your county. That way, you don’t get over-warned. That’s probably the best way to get woken up in the middle of the night in the event of a tornado warning.”

There have already been several tornadoes in Iowa this year, following 51 twisters in 2011. Johnson encourages Iowans to take weather warnings seriously and find a safe place to go when they’re issued. “Generally speaking, if it’s a severe thunderstorm warning, what I personally do is check the warning and see what the hazard is. If it’s high winds above 70 or 75 miles per hour, I may choose to go down to my tornado shelter. If it’s just some one inch hail, maybe not, maybe I’ll just stay inside the house,” Johnson said. “That’s the best thing to do – just know the hazard and take the correct action.”

The NIU study found that from 1950 to 2005, just 27% of U.S. tornadoes were nocturnal, yet 39% of all tornado fatalities occurred at night.