The winter storm in the US over February 1 and 2 is estimated to cost insurers between $US790 million ($787 million) and $US1.4 billion ($1.39 billion) according to Boston-based catastrophe modeller AIR Worldwide.

The storm was one of the worst since the 1950s, cutting across Texas and reaching Canada. It affected nearly 100 million people in 30 states.

AIR’s estimate of insured losses includes damage to property and vehicles, business interruption losses and additional living expenses for residential claims.

It says many flat-roofed commercial structures collapsed under the weight of sleet, rain and snow.

The storm was able to form when cold Arctic air pushed south from Canada and moist air streamed north from the Gulf of Mexico. Its force was magnified by the unusual strength of a high-pressure system.