With an especially busy travel season underway, the polar vortex is back, making the weather a mess

Winter storms have arrived just in time for what is expected to be a busier holiday travel season than last December.

On Saturday, snow blanketed a swath of the Rockies, grounding hundreds of flights, while freezing rain created havoc on roads in the mid-Atlantic. Icy conditions contributed to hundreds of auto accidents across the country, and at least nine deaths were reported.

In Denver, airlines canceled more 300 flights after nearly 8 inches of snow hit the metro area.

“We’re in mop-up mode and trying to get caught up, but it’s been bad,” said Heath Montgomery, a spokesman for Denver International Airport.

Initially weather reports suggested that Denver would receive 1 to 3 inches of snow overnight, but that total was quickly surpassed by early Saturday morning.

“Mother Nature really threw us a curveball,” Montgomery said. Warmer temperatures were expected Sunday and into the early part of the week.

Winter storm warnings stretched from the central Rockies to parts of the upper Midwest, according to the National Weather Service. On the East Coast, a mix of snow, freezing rain and sleet fell from Boston to Washington.

At Washington Dulles International Airport, all runways were closed for nearly four hours early Saturday morning because of the icy conditions.

This holiday season, nearly 93.6 million people will take a road trip, an increase of 1.5% over last year, according to the American Automobile Assn. Air travel, meanwhile, is expected to increase by 2.5%, with more than 6 million people flying to their holiday destinations over the next two weeks.

The dip in temperatures was the result of a southward shift in the polar vortex, a large area of low pressure and cold air that swirls around the north and south poles year-round, according to the National Weather Service.

Back in Denver, Montgomery said the airport had dispatched nearly 500 workers to clear runways and de-ice planes as airlines resumed service.

“This is a busy time for us, so we need to keep the airport clear,” he said.

kurtis.lee@latimes.com

Twitter: @kurtisalee

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