Much of the U.S. is dealing with severe weather during one of the busiest travel times of the year. A potent winter storm threatened blizzard-like conditions, treacherous travel, and power outages in parts of the Upper Midwest as other areas of the country braced Monday for plunging temperatures, strong winds and a mix of snow, ice, and rain.

The snow and strengthening winds began spreading Sunday across the Northern Plains, where the National Weather Service warned of whiteout conditions and possible blizzard conditions that could make travel impossible in some areas.

Travelers nationwide have already been struggling to get to their destinations as wintry weather slammed many parts of the country.  In the Midwest, drivers struggled to stay on the roads amid heavy snow and blistering winds. In Iowa, close to the Minnesota border abandoned vehicles littered roadways making conditions even more hazardous. Winds gusted up to 50 miles per hour.  

These conditions pounded much of the Midwest and Great Lakes. Ice blanketed parts of Indiana and Illinois. Heavy snow also hit much of Wisconsin.  

That same system is now headed to the Northeast, packing a one-two punch to a region still digging out from the biggest snowstorm that parts of the area have seen in nearly four years, surprising some New York City tourists like Kolby Gray and his wife.

"We're from West Virginia," he said. "We're here for our three-year anniversary, which was yesterday. We realized it was going to snow like heck. We didn't even think it was coming."

Some Big Apple visitors, such as Jennifer Yokley, welcomed the wintry weather. "I think it's absolutely beautiful," she said. "We're from North Carolina, so it was great to come up to New York and see the snow."

Brutal weather conditions snarled air travel as thousands of flights have been canceled. Holiday travelers were stuck as they tried to get back home after Christmas or to vacation destinations. Ron Dow was trying to get to Hawaii from Boston's Logan Airport.

"They cancelled our flight to JFK, which of course we missed our connecting flight," he said.

Thousands of other flights have been delayed, frustrating weary travelers.

Meanwhile, on the West Coast, parts of California are buried in mud as heavy rains battered the area for days. Many roads and highways are closed due to mudslides, making driving impossible. In the mountains near Big Bear Lake, five people were hurt, including two children when a massive boulder crashed into Highway 18, worrying drivers that more could be on the way.  

Coast to coast, weather woes are making travel difficult on this all-important week between Christmas and New Year's Day.