April showers might bring May flowers, but those showers could evolve into house-rattling thunderstorms. As part of Severe Weather Awareness Week, Iowans are being reminded about the dangers of such storms. Meteorologist Jeff Johnson, at the National Weather Service’s Des Moines office, says there’s a set criteria they follow to determine if a storm will be declared as a "severe" thunderstorm.

He says storms must be producing hail at least three-quarters of an inch in diameter, winds in excess of 58-miles-per-hour, or both. Johnson says straight line winds, which often accompany thunderstorms, can cause a lot of damage — to trees, to shingles on the roof, and elsewhere. Johnson says Severe Thunderstorm Warnings are not to be taken lightly.

He says, "Treat them like a tornado warning. At a minimum, get inside, get away from windows, get off the water and head indoor when you hear a Severe Thunderstorm Warning." Johnson says tornadoes can sometimes spin out of a severe thunderstorm with virtually no warning, so it’s a wise idea to take cover.

"The best place would be the bottom story, preferably below ground or a basement and the interior of the house with as many walls between you and the tornado in a small room would be best," he says. For more information about Severe Weather Awareness Week, visit the National Weather Service website .