An April snowstorm dumped up to 20 inches over Wisconsin and Minnesota, knocking out power to thousands of homes and contributing to several fatal traffic accidents.

At least four deaths were blamed on snowy roads in Minnesota, including a 17-year-old boy who was killed when the car he was driving to his prom slid into a ditch and overturned.

At the height of the weekend storms, some 57,000 electricity customers in Minnesota and some 40,000 customers in Wisconsin lost power.

The most snow fell in the northeast Wisconsin town of Elcho, which received 20 inches as the 140-student Elcho High School celebrated its prom Saturday night.

"The power kept flashing out, and the speakers with the music kept going out," 16-year-old Kelsey Wolff said. "It was called 'A Night to Remember.' We were all laughing about that."

In Minnesota, authorities said a 44-year-old woman died when her car slid into a van, a 60-year-old woman died when her minivan collided with a pickup, and a 72-year-old man was struck and killed by a sport-utility vehicle when he tried to cross a roadway on foot after his car stalled.

In Minnesota, more than 2,500 customers were still without electricity Monday morning in the Minneapolis-St. Paul area, according to Xcel Energy.

About 10,000 homes and businesses were still blacked out Monday morning in northern Wisconsin, and Wisconsin Public Service Corp. said some 4,000 customers might not be restored until Tuesday.