Tornado Alley's eastward drift upends cat bond loss assumptions

Verisk data, reported by Carrier Management, show 220 confirmed tornadoes in Illinois by the end of July. That is a state record, and it already eclipses the state's 2024 and 2025 totals combined. Indiana and Wisconsin set records too. Since 2022, the average severity of an Illinois tornado has quadrupled.

Nationally, tornado claim volume has fallen every year since the 2023 peak. The average estimated reconstruction value has climbed every year since, and now sits 72% above the 2022 level. Illinois's surge is the state's third distinct spike in five years. It is concentrated in Cook, Kankakee and Coles counties, where Kankakee's average estimated damage is $104,000. Wisconsin's count rose 672% year over year, but nearly all of that came from one July event in Winnebago County.

Tory Farney, vice president of Verisk Weather Solutions, told Carrier Management that the eastward expansion is measurable and strongly evidenced, though whether it lasts is 'still a point of uncertainty.' A warming climate that carries warmer, more humid air farther north and east is one suspected cause. The more pressing issue is that the new touchdown zone is more heavily populated. Verisk's figures show losses are worse when storms strike there.

ILS investors should weigh the severity of eastern storms as heavily as their frequency. A cat bond or collateralized reinsurance contract whose modeled tail still assumes the old Tornado Alley geography may be underpricing the risk of a Cook County event. With three Illinois spikes in five years, the claims data give sponsors and investors a concrete input for repricing that eastern exposure before the next renewal season, and for judging how much of the shift is permanent. If the pattern reverts, models that priced the shift as permanent will overestimate the peril.