Aon estimates May SCS losses among costliest in US history

By Rebecca Delaney

May 22 - (The Insurer) - Insured losses from severe convective storm (SCS) activity across several U.S. states from May 14 to 20 are expected to total billions of U.S. dollars, with the St Louis tornado alone generating $1.6 billion, according to estimates from Aon.

An event update issued by the broker on Thursday pegged total economic and insured losses from hail and wind damage sustained over the central and eastern U.S. from May 14 to 17 as "well into the single-digit billions" of U.S. dollars.

The majority of these losses are attributed to a EF-3 tornado that hit St Louis, Missouri, with city officials offering an initial estimate of $1.6 billion in total damages.

Extensive tornado and hail damage was recorded across the Ohio River Valley and the Midwest region, including Colorado, Nebraska and Kansas. Thunderstorms were most severe in Wisconsin, Michigan and Illinois.

Aon said that as more assessments are completed in the coming weeks, the four-day severe weather outbreak may potentially rank among the costliest in U.S. history on a price-inflated basis.

In addition, total economic and insured losses from a severe weather outbreak over the central Great Plains between May 18 and 20, including multiple significant tornadoes and widespread wind impacts, are also expected to reach into billions of U.S. dollars, Aon said.

Combined, the two outbreaks over the past week are already among the most expensive severe weather events so far in 2025.

For comparison, Aon noted that the outbreak from March 14 to 16 earlier this year already ranks as the seventh costliest severe weather event in U.S. history, with economic losses of $6.3 billion and insured losses of $5 billion.

In a LinkedIn post on Monday, BMS senior meteorologist Andrew Siffert said that the SCS activity from May 16 to 18 will likely result in insured losses of around $5 billion.

Siffert said this would take the tally of insured losses in the U.S. from SCS activity to around $20 billion for the year to date.