Storms and tornadoes that killed eight people in the US midwest on November 17 could generate insured losses of more than $US1 billion ($1.08 billion), risk modeller RMS says.

There were 81 reports of tornadoes, mostly in Indiana and Illinois, plus hail and high winds, with 17 reports of hurricane-strength gusts.

In Michigan, more than 530,000 homes and businesses were left without power.

In Illinois 250 to 500 homes were destroyed, with the town of Washington, near Chicago, particularly badly hit.

Until these storms it had been a relatively quiet year for US tornadoes, with 903 reported, well below the average total to November 18 of 1424, RMS says.

The Insurance Information Institute says November is usually one of the least active months for tornadoes, with May most active.

A tornado in Moore, Oklahoma, on May 20 caused $US1.6 billion of insured damage.

RMS says the November 17 storms could cause the second-highest insured loss from severe storms this year, after the Oklahoma events.