While frigid air settles over most of the US, the Northeast braces for snow

On By Littum

The coldest air of the season so far will sweep across the United States this weekend, producing a blanket of snow in the Mid-Atlantic and Northeast on Sunday, bringing below-freezing temperatures with dangerously gusty winds to much of the country. Monday’s inauguration of President-elect Donald J. Trump on Monday is likely to be one of the coldest inauguration ceremonies in decades.

“The cold air is coming straight from the Arctic and will rise south through Canada and into the United States over the weekend and into early next week,” said Alex Lamers, a meteorologist at the National Weather Service’s Weather Prediction Center.

Cool temperatures in January are not unusual, but these conditions are likely to be unseasonably cold. The cold will slowly settle across the country, starting in the upper Midwest on Saturday, dropping more than 30 to 40 degrees from earlier in the week, before moving toward the southern and eastern seaboard on Sunday.

As the cold air trudges across the country, a storm system off the East Coast could combine to bring a burst of wintry weather Sunday. There is a moderate chance of three to six inches of snow falling from Washington DC through New York City and up to Boston.

Gusty winds will remove body heat, making you feel even colder if you’re outside. The Rocky Mountains, the Northern Plains and the Upper Midwest could see wind chill temperatures drop to 30 to 50 degrees below zero at times Saturday through Tuesday. A cold that poses an increased risk of hypothermia and frostbite on exposed skin, forecasters from the Weather Prediction Center warned.

On Monday, nearly every state will experience temperatures that are colder than average for this time of year.

Daytime temperatures on Monday will likely be 20 to 40 degrees below average from the Rocky Mountains to the Appalachians. It will be so cold, said Mr. Lamers that “counting the tops of the volcanoes in Hawaii, at least part of every state should be below freezing by Monday morning.” More than 250 million people across the United States are likely to feel freezing conditions at some point in the next week, he said.

It will probably be the coldest air of the season in many areas. In Chicago, the current National Weather Service forecast calls for wind chills of 20 below zero on Monday. (That’s cold, but about normal for the city, where O’Hare International Airport has recorded a low in 32 of the past 40 winters.)

As of Thursday, it looks like the cold will most likely peak Monday and Monday night in terms of the total area affected and the intensity of the cold over the central and northern United States. Whenever an arctic air mass like this dips all the way to the Gulf Coast, forecasters like Mr. Lamers it carefully because it increases the potential for rare winter precipitation in the south. It was too early to say for sure, but there is at least some chance of snow or ice in the south next week.

Next Thursday, temperatures will still be cool, but are expected to warm up to something closer to normal. Overall, through the end of next week, some regions may still experience below-normal temperatures, but it shouldn’t be as cold as Monday through Tuesday.

It was 48 degrees Fahrenheit at noon on January 20, 2017, when Mr. Trump was first sworn in as president. This time he can take the stage during one of the coldest inaugurations in decades.

Temperatures in Washington, DC, will begin to drop on Sunday, and wind gusts of up to 30 miles per hour are expected to sweep through the National Mall on Monday. With temperatures already below freezing, the wind will make the open space in front of the US capital feel much colder, said Jeremy Geiger, a forecaster with the National Weather Service in Washington, DC

The wind chill is expected to reach 5 degrees in the city early Monday morning, a benchmark the city hits at least once most winters, Mr. Lammers.

While it will be cold, it won’t be the coldest initiation ever. President Ronald Reagan’s second swearing-in ceremony – on January 21, 1985 – was moved indoors and the parade was canceled due to the bitter cold.