CHICAGO: A monster U.S. winter storm pounded the Northern Plains and Upper Midwest on Thursday, killing a firefighter, knocking out power to more than 900,000 people and canceling or delaying thousands of flights.

A broad swath of the northern United States from Washington state to New England remained under winter weather advisories with another 18 inches (46 cm) of snow, winds up to 50 miles per hour (80 kilometers per hour) and wind chills equivalent to minus 40 degrees Fahrenheit (minus 40 Celsius) possible throughout the day, the National Weather Service said.

A volunteer firefighter was killed in suburban Grand Rapids, Michigan, after coming in contact with a live power line knocked downed by ice, local officials said on Twitter.

Some 900,000 homes and businesses were left without power in

Illinois, Indiana, Michigan, New York and Wisconsin on Thursday morning, according to Poweroutage.us.

More than 2,000 flights were canceled and another 15,000 delayed due to the heavy weather, according to flight-tracking website Flightware.com. Many roads were left impassable or treacherous to drivers.

"Travel on the roads can be dangerous with just a trace of ice. But we're seeing ice caking from a quarter to half inch (6 mm to 1.3 cm)," said Richard Bann, of the weather service's Weather Prediction Center in College Park, Maryland. "That can be practically impossible."

Snow fell at a rate of 1 to 2 inches (2.5 to 5 cm) an hour in Minneapolis, home to about 2.9 million people. New accumulations added to the 8 inches of snow already dumped by the storm.

Video footage and photographs on social media showed cars stuck on roadways, while streets and walkways were covered in drifting snow.

"Big-time flakes coming down here," storm chaser Aaron Jayjack said in a video he posted on Twitter from Minneapolis. "This is the final push of the storm, and in fact appears to be heaviest snowfall yet."

The Minneapolis school system was holding classes remotely for more than 29,000 pupils for the rest of the week. Dozens of school districts also canceled classes in North and South Dakota, Colorado, Michigan and Wyoming

In Ann Arbor, Michigan, home of the University of Michigan, almost 20,000 homes and businesses lost power. Nathan Pietryga, manager of the long-standing college hangout Pizza Bob's, counted himself one of the lucky ones.

"I made it to work, a little shuffling on the ice," he said.

Classes weren't canceled, but students were advised to use discretion. Pietryga indicated he expected to sell some pizza. "We've been here forever, the kids will come in," he said.

A separate storm spawned unusual weather in California, where much of the state was under high wind and winter storm warnings.

Rare snow flurries were reported in San Francisco while blizzard conditions were expected in high elevations, even in the typically balmy Los Angeles area. By Saturday, up to 8 feet (2.4 meters) of snow could accumulate on Mount Baldy, about 45 miles (72 km) east of Los Angeles in the San Gabriel Mountains.

At the same time, parts of the Ohio Valley and the South could see near record-breaking high temperatures, beginning Thursday and lingering into the weekend. Weather forecasters predicted temperatures to hit 88 F (31 C) in Jacksonville, Florida on Sunday.