After Illinois Tornado Outbreak, a Question Lingers: Is Chicagoland getting more Tornadoes?

By Linus Höller (Linus Hoeller)

Title image: A severe thunderstorm moves across the landscape near Big Rock, IL during the March 31, 2023 outbreak. (Linus Höller/TWU)

Severe storms swept across much of the central United States on March 31st, killing at least 33 people, injuring over 211 more and causing significant property damage, including leaving over 766,000 customers without electricity. While outbreaks of this sort are not unheard of, some scientists are warning that it could be a symptom of broader trends in severe weather – including more tornadoes in the Chicago area – as human-induced climate change upsets global weather patterns.

With 142 confirmed tornadoes, hail of up to 9 centimeters in diameter and gusts reaching 160 km/h, meteorologists say the outbreak is one of the most significant in living memory. Whether the March 31st outbreak was directly linked to climate change, however, is hard to determine, said Jana Houser, a professor at the Ohio State University whose research focuses on tornadoes.

“That significant tornadoes happen so far north so early is unusual,” said Houser. “But it’s also not out of the realm of historical possibilities – just probabilistically unlikely.” She and other researchers who spoke on the topic pointed to the April 11, 1965 Palm Sunday outbreak as well as the series of storms on April 3, 1974, which resulted in at least 148 confirmed tornadoes, including in Illinois and other parts of the Midwest. And in April 1967, Chicago itself was hit by a tornado during an outbreak.

An interactive map showing the 22 confirmed tornadoes happening in the NWS Chicago office’s area. (Linus Höller/TWU)

While Houser stressed that while research was in its infancy, she saw some indications that tornadoes may become a more frequent fact of life in the Midwest due to climate change. She said a warmer planet may shift the area of temperature gradient between warm air from the gulf and cold air over Canada farther north than it had been previously – bringing tornado conditions to Illinois and neighboring states, particularly in early spring.  

“We’re on the edge of unusual,” said Harold Brooks of NOAA’s Severe Storms Laboratory about the timing of the outbreak. “This is early for y’all in the Chicago area.”

NIU professor Vittorio Gensini, too, said he thought the event was unusually far north for this time of year. He said there was a surprising amount of moisture in the air that day. “Part of that, I think, is the Gulf of Mexico, which is running anywhere from 4 to 6°F above average currently. A warm gulf – that could be a fingerprint of climate change,” he said.

Research conducted by Gensini and Brooks and published in 2018 showed that while nationwide counts of tornadoes have stayed constant since 1979, the areas they occur in have changed. Their paper states that “robust positive trends have been documented in portions of the Midwest and Southeast United States.”

“If you take a time series in Chicago,” said Gensini,” your risk of being hit by a tornado is actually going up.”

The occurrence of more frequent tornadoes east of the Mississippi is of concern primarily for human reasons: There are simply more people there than in the Plains, Gensini said. This raises new issues for communication, building codes and emergency response.

While forecasts are getting more and more accurate, “a forecast is not a good forecast unless someone receives it and takes action on it,” said Gensini. “That’s the social science aspect of this.”

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