Severe Weather Preparedness Week: Tornadoes

CHICAGO (WLS) -- This week is Severe Weather Preparedness Week in Illinois. ABC7's Larry Mowry takes an in depth look into tornado climatology.

Tornadoes can happen any time of the year and any time of day. But there is a favored time of year and even a favored time of day when tornadoes are most likely to occur. Location matters too, and in the Midwest tornados are common.

Illinois averages 54 tornadoes a year. Only the states in the Central and Southern Plains and Florida average more.

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An Active jet stream coming over the Rockies and warm Gulf moisture flowing north are the ingredients which make our area a prime location for storms.

Last year, an EF-3 tornado hit Naperville and before moving to Willow Springs . And the Naplate to Ottawa tornado which was an EF 3 in 2017.

Tornadoes are a big threat in the spring, but they can come at any time.

Mike Bardou is a meteorologist with the National Weather Service office in Romeoville.

"There are distinct seasons and for tornadoes we see the peak from about April to August. Though we have had tornadoes any time of year. In terms of time of day, between about 3 and 9pm is really where we see those peaks," said Bardou.

This graph shows that May and June historically have had the most tornadoes

But what about Lake Michigan? There is a myth that the lake protects against tornadoes, but experts say, that isn't true.

The lake does not provide any reliable protection from tornadoes. Historically speaking, we've had a lot of tornadoes in the city limits or right around the counties by the lake.

One of the most recent tornadoes was back in August of 2020 when an EF 1 came through the Rogers Park area and went all the way to the lakeshore.

In September 2019, an EF -1 tornado also struck Waukegan and continued out into the lake as a waterspout.

In fact, when you look at the number of tornadoes reported in surrounding counties since 1950, there is no buffer created by the lake. Cook County has seen 58 tornadoes since 1950, the most of any county. There are a couple of reasons for this. First, it is one of the larger counties in the area. And second, even the small, weak tornadoes are seen by someone or hit something in such a populated area. A small tornado touching down in a field may never get counted .

So as we head into Spring, now is the time to get prepared. Think about what you're going to do, how are you going to get weather information, how you're going to get warnings, and what you're going to do when those things are actually coming out.

It's important to remember the difference between a watch and a warning. A watch means conditions are possible for a tornado. A tornado warning means one has been spotted and you need to take shelter now.