Amidst unusually warm weather in the Upper Midwest, severe thunderstorms and tornadoes wreaked havoc across Iowa, Illinois, and Wisconsin on Thursday. This unexpected episode saw the formation of at least three tornadoes and multiple reports of large hail, marking an alarming trend in winter weather patterns.

Southern Wisconsin experienced the most intense twister, making it the state's first-ever recorded tornado in February. The storms were fueled by temperatures that soared nearly 30 degrees above the average, breaking numerous records. This pattern of severe thunderstorm activity in winter months is believed to be a consequence of human-caused climate change, according to scientists.

Reports of tornadoes came in from Marshall County and Putnam County in Illinois, where significant damage occurred, including an overturned semi-truck. Meanwhile, Chicago witnessed a dramatic display of lightning accompanying the thunderstorms. Further severe weather, with a possibility of additional tornadoes, is expected in the Deep South this weekend, followed by the Southeast early next week.

In Wisconsin, the tornado appears to have traveled a significant distance on a southwest to northeast path, approximately 15 to 20 miles south of the state capital, Madison. Preliminary assessments suggest the damage is consistent with a tornado of at least EF1 strength, possibly reaching EF2 on the intensity scale.

The tornado's distinct characteristics, with a fully condensed funnel reaching the surface, indicated a relatively dry atmosphere and high cloud bases. Meteorologists are currently surveying the wreckage, which includes snapped power poles, tree damage, and roofs missing from numerous homes.

The tornado's formation began with a low-pressure system over Minnesota that drew air from all directions. Warm air and a hint of moisture were pulled northward from the south, while cold, dry, and dense air surged southeast from the north. These opposing air masses converged along a cold front, resulting in the severe storm conditions.

Moisture levels were initially anticipated to be insufficient to support tornado activity. Typically, tornadoes require higher humidity levels, measured by dew points in the 60s and 70s. However, on Thursday evening, a small pulse of moisture from the south along a warm front raised dew points to the 50s, allowing for the tornado's formation.

The National Weather Service issued a record-breaking five tornado warnings for southern Wisconsin during February's severe storms. Both convective available potential energy (CAPE), the storm fuel, and wind shear, which promotes atmospheric spin, were crucial factors. While the available fuel from moisture and warm air was marginal, it exceeded typical levels for this time of year due to climate change.

Thursday's unprecedented warmth shattered numerous temperature records across the Upper Midwest. Wisconsin, in particular, experienced temperatures exceeding previous daily records by as much as 10 degrees. For instance, Eau Claire reached 59 degrees, surpassing a previous daily record of 49 degrees. Similarly, Monroe recorded 58 degrees, well above the average high of 28.9 degrees for this time of year.

As climate change continues to influence weather patterns, the propensity for unseasonably warm and humid air to travel north during the winter months is intensifying. This, in turn, increases the likelihood of thunderstorms and tornadoes during what was once considered a quieter season. A previous outbreak in December 2021 already saw the emergence of tornadoes in western and central Iowa and parts of Minnesota, marking a historic shift in severe storm distribution.

A recent study published in January 2023 supported these findings, projecting an escalation in supercell thunderstorms capable of producing tornadoes outside of the traditional severe storm season, including late winter. As our climate continues to change, the implications for severe weather events demand heightened attention and preparedness.