Severe Weather Awareness Week: Tornadoes

CEDAR RAPIDS, Iowa (KCRG) - Iowa is no stranger to tornadoes. Our state has an average of 48 tornadoes each year. The most in a single year was 120 in 2004, and the fewest was 16 in 2012.

The number of tornadoes begins to increase in April, with the majority coming in May and June. The number begins to trail off again in July and August. They can happen in every month of the year, though!

Tornadoes are most common in the afternoon and evening. Tornadoes do sometimes happen at night, and those can be especially dangerous because most people are asleep and aren’t aware of approaching weather. In addition, nighttime tornadoes are difficult to see.

Tornadoes are given a rating based on the worst damage they cause. That rating comes from the Enhanced Fujita Scale, which goes from zero to five. Most of our tornadoes are, fortunately, on the weaker end of the range. More than half are EF0, which will peel away some siding and shingles and break branches off trees. If your house is hit by an EF0, you’re still going to have damage to deal with and you may not consider it “minor” damage. EF5 tornadoes are the most violent and will sweep even well-built homes off their foundations and can throw vehicles as far as a mile away. In 2008, some of the tornado damage in Parkersburg was rated EF5.

EF0 tornadoes are typically on the ground for a short time. More intense tornadoes often are on the ground longer, although they won’t have the same strength the entire time. On average, an EF0 tornado is on the ground for less than a mile, while EF4 and EF5 tornadoes travel well over 30 miles.

Tornadoes can sometimes spin up along a “squall line,” which is a long line of thunderstorms that typically produces strong winds. Tornadoes within a squall line can be hard to predict and may not be detected until they’ve already come and gone. This is why you should still take severe thunderstorm warnings seriously! Fortunately, newer radar technology helps us do a better job of seeing those quick tornadoes to give enough time to warn people that this type of tornado may be developing.

Since 1980, Iowa tornadoes have killed 30 people and injured more than 800 people.