Anderson Cooper 360

What is a derecho?

A fast-moving storm system struck parts of the Upper Midwest hard on Wednesday evening, delivering blows to Chicago and many other communities before moving quickly to inflict damage farther east.

The Windy City itself experienced gusts that measured about 50 mph around 6 p.m. (7 p.m. ET), in addition to dime-size hail, the National Weather Service's Chicago branch said.

Cities and towns near Chicago were affected as well.

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