A series of severe storm outbreaks stretching from the US Mid-Atlantic northwest to the Canadian prairies are expected to generate insured losses running into the billions of dollars, according to Aon's latest catastrophe report.
The outbreak began on June 5 with storm systems tracking from the Rockies and Great Plains to the Mid-Atlantic. Between June 5 and 8, a series of systems brought large hail, heavy rain and winds exceeding 90 mph, causing isolated flash flooding and significant tree damage, including one fatality in New York City.
More than 2,000 trees were downed or damaged in New York City alone on June 6, while four-inch hailstones were recorded in Colorado and peak gusts exceeding 90 mph were measured in both Kansas and North Dakota.
The most destructive phase ran from June 9 to 11. Successive bowing lines of intense thunderstorms struck northern Illinois, southern Wisconsin and northwest Indiana, with gusts reaching 94 mph in Wisconsin. The widespread wind damage tore off roofs, shattered power lines and left more than 500,000 customers without power. Multiple large tornadoes flattened buildings and heavily damaged vehicles in communities south of Chicago, including Streator, Illinois, and Hobart, Indiana, while an EF-1 tornado damaged dozens of homes in Freeland, Michigan.
Canada was also severely affected. Parts of Manitoba and Saskatchewan received 9.8 inches of rain and four-inch hail, triggering severe flash flooding that washed out highways, displaced 150 residents in the Swan Valley region and knocked out power to 25,000 customers.
Aon said the majority of the week's financial impacts are expected to be attributed to the June 9 to 11 outbreak, given the extensive damage across the Midwest.
The June outbreaks land at a particularly sensitive moment for US property insurers.
Tornadoes, hail, straight-line winds and severe thunderstorms caused US$51 billion in US insured losses in 2025, marking the third consecutive year such losses exceeded US$50 billion, more than any other category of natural disasters, according to the Insurance Information Institute.
Aon's own annual Climate and Catastrophe Insight report found that severe convective storms have overtaken tropical cyclones as the costliest insured peril of the 21st century, generating US$61 billion in global insured losses in 2025, the third-highest annual total on record for the peril.
The accumulation problem is as significant as any single event. A survey of American Property Casualty Insurance Association members found that 87% of respondents expressed significant or some concern over future severe convective storm losses. When asked to rank perils by potential impact on annual earnings after reinsurance recoveries, respondents placed severe convective storms at the top, ahead of fire, hurricanes, wildfire and flood.
Reinsurance structures are also under pressure. High attachment points in reinsurer contracts leave primary insurers exposed to substantial losses from frequent severe convective storm events.
Between January and September 2025, the US experienced 39 such events with average insured losses exceeding US$1 billion per event. Tehya Duckworth, senior vice president and property treaty reinsurance team lead at Munich Re Specialty North America, said that terms tightened in 2023 with higher attachment points and retention levels for severe convective storm risks, but that inflation and growing exposures are eroding those changes, suggesting further increases in attachment points may be needed.
The pricing consequences for homeowners are already significant. US home insurance premiums are projected to increase a further 4% in 2026, marking a fifth consecutive year of rises. Since 2021, premiums have climbed 46%, roughly three times the rate of inflation.
In 2025, six states saw premiums jump by more than 20%, including Minnesota at 34% and Colorado at 33%. In certain regions, capacity withdrawals from admitted markets have created opportunities for excess and surplus lines carriers and reinsurance-backed structures to fill the gap.
The Chicago metropolitan area, at the center of much of the June damage, carries the highest urban hail exposure in the US at US$1 trillion in reconstruction cost value, a concentration that reinsurers and primary carriers are watching with increasing concern.
