Tornados in Illinois are increasing, and climate change may play a role, weather experts say

As Illinois puts an unusually tornado-dense year behind it, there is growing evidence that they are not only becoming more frequent and damaging, but that their range is changing in ways that could have repercussions in Illinois and states to the east.

Some studies have shown that a portion of the area that has colloquially been referred to as “tornado alley” has had fewer tornadoes while areas east of the Mississippi River have had more.

Climatologists say the concept of a tornado “alley,” or lane where the storms are most common, is a bit of a misnomer. It's more like “tornado country,” they say, historically encompassing Kansas, Nebraska, Iowa, Oklahoma and northern Texas and reaching east to the Appalachian Mountains. That area itself, weather experts say, isn't shifting, but they are seeing more tornadic activity in the more populated states to the east, and that means an increased risk of injury, death and property damage.

“We have high tornado frequency in the kind of Plains area that we think about as tornado alley, but we also have really high tornado frequency in the Mid-South and Midwest. It's not really a tornado alley, it's just this is where tornadoes occur,” said Illinois state climatologist Trent Ford. “Essentially, from the Rocky Mountains to the Appalachian Mountains, that's your hotspot of tornadoes globally, not just in the U.S.”

According to data released by the National Oceanic and Atmospheric Administration this summer, 115 tornadoes touched down in Illinois from May 1, 2022, through April 30, 2023 — leading the country.

The year's tornadoes were the most recorded in that 12-month time frame since 2006, NOAA figures show. Two years prior, 141 tornadoes were recorded from May 2003 through April 2004. That's compared to the state's average over the past 20 years, which is just under 70 tornadoes a year.

The upward trend in tornadoes — which can only be reliably tracked beginning in the late 1970s with the advancement of weather satellite technology — is difficult to explain, said Victor Gensini, a professor in the Department of Earth, Atmosphere and Environment at Northern Illinois University.

One part of the answer could be what is called “interannual variability,” that is climate factors that change on a 10- to 20-year cycle, causing increases and decreases in tornadic activity. Another part could be climate change.

“We suspect that some of it — perhaps a lot of it — has to do with climate change. That's because a lot of our climate projections show that in the future, we will have environments that are more supportive more frequently for tornadoes in the areas that have already seen increases,” Gensini said. “There's likely some component of climate change, but kind of disentangling how much is due to climate change, and how much is due to this other variability is really difficult.”

Gensini is a co-author of a 2018 study that documented “robust positive trends” of tornado frequency in portions of the Midwest and Southeast United States.

“The increasing frequency east is a really big deal for vulnerability in disasters,” Gensini said. “The reason you're seeing more and more of these disasters is because we have the same number or more of tornadoes in places that actually have assets and people in the way, and that's a really big deal.”

The risk associated with tornadoes in Illinois is also increasing due to sheer population growth and development — whether climate change plays a role or not, Ford said.

“We don't really need to quibble about the impact of climate change on tornadoes to put into solutions that make us less vulnerable to tornadoes,” Ford said. “The Chicagoland area is growing in its size and its population, which means that if a tornado occurs today in the Chicagoland area or the seven-county area, it is a lot more likely to hit something that we care about than it was 30 or 50 years ago.”

For example, though the F-5 tornado that ran through Plainfield in 1990 devastated the area, resulting in 29 deaths and $160 million in damage, Ford said the same tornado would likely even cause a significant amount more damage if it occurred today.

While researchers have a long way to go before climate models can accurately predict tornado trends, solutions to address increasing vulnerability should be the priority no matter what the trends say.

“There's a lot of uncertainty with those trends and a lot of work that needs to be done, but we know that the way that cities are being developed now is increasing the vulnerability to those tornadoes far more than any kind of climate change trend,” he said. “Hopefully reducing the vulnerability we have can make us resilient to any kind of changes to tornadoes that come down the line.”

Those solutions include addressing housing insecurity by establishing a denser network of tornado shelters, as well as buffing up residential and commercial building codes to better fortify against potential storms.

Jenny Whidden, jwhidden@dailyherald.com, is a climate change and environment writer working with the Daily Herald through a partnership with Report For America supported by The Nature Conservancy. To help support her work with a tax-deductible donation, see dailyherald.com/rfa.