ARLINGTON, Va. − A deep freeze that settled in across much of the nation Sunday threatened to wallop dozens of states with snow and ice, bring freezing temperatures as far south as Florida and create chaos for travelers, football fans and even voters in the Iowa Caucuses.

Wind chill advisories or warnings were in effect Sunday for more than 100 million Americans, and over 44 million were under a winter weather advisory. Much of the country faced temperatures 20-40 degrees below normal. Parts of North Dakota could see "life-threatening wind chills as low as 60 below zero," the National Weather Service said.

A winter storm with snow and ice will threaten the mid-Atlantic and New England from Monday night to Tuesday night, AccuWeather said. The storm, and a wall of arctic air, is expected to ride the jet stream across most of the nation over the next few days.

"For much of the country, this will end up being the coldest and most persistent outbreak of arctic air in a couple of winters," AccuWeather Senior Meteorologist Matt Benz said.

Developments:

∎ More than 6,500 flights within, into or out of the U.S. were delayed or canceled as of 3 p.m. ET Sunday, according to the monitoring website flightaware.com. More than 10,000 flights were similarly affected Saturday.

∎ In Washington, D.C., Mayor Muriel Bowser was planning to activate a Cold Weather Emergency on Monday through Thursday. Human services agencies will assist unsheltered and vulnerable residents with shelters, warming buses, gloves, blankets and handwarmers.  

∎ In Arlington, outside of the nation's capital, deep freezes are rare and authorities urged residents to consider wrapping pipes or leaving water running a trickle to avoid freezing and cracking: "Temperatures expected to drop this week. Think of the pipes."

Snow and ice from Texas to Tennessee

Snow rolling across Texas, Oklahoma and southern Kansas on Sunday was forecast to expand into Arkansas, Missouri, the Tennessee Valley and the southern Appalachians through Monday. Some areas could see more than a foot of snow, AccuWeather said. An area of dangerous ice was forecast late Sunday in Texas and southeastern Oklahoma before spreading into Louisiana, Mississippi, southern Arkansas, Alabama, Georgia and Tennessee into Monday.

"Texans are urged to take precautions to protect themselves, their loved ones, and their homes," Gov. Greg Abbott said Sunday.

3 feet of snow, 50-mph winds

In the Northeast, Buffalo was under siege and an NFL playoff game scheduled for Sunday was postponed. The National Weather Service said a band of lake-effect snow would dump 1 to 2 feet across much of the area, and some communities could see up to 3 feet. Winds gusts of up to 50 mph would prompt near-blizzard conditions, the weather service warned.

"Travel will be very difficult to impossible at times with deep snow cover on roads," the advisory said. "Widespread blowing snow will reduce visibility to near zero."

Iowa, where iconic political caucuses are scheduled for Monday, was setting temperature records Sunday. The temperature at 7:30 a.m. dipped to minus 18 degrees at Des Moines International Airport, the lowest temperature recorded for a Jan. 14 in Des Moines since 1888. It's also the lowest temperature recorded since a minus 20 reading in January 2019.

"Many roads have drifted shut or partially shut overnight," the weather service in Des Moines warned on social media Sunday. "Do yourself and the road crews a favor and do not travel!"

Parts of northern Florida are projected to trend from a daytime high near 70 degrees on Monday to the upper 40s by Wednesday. Overnight temperatures could drop below freezing across the northern third of the state, AccuWeather warned.

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In Iowa, heroism of first responders aids woman in labor

Deputies in Marshall County, Iowa, worked with other first responders to aid a woman who gave birth in the snowstorm early Sunday. The call for help from a woman who was having contractions came shortly before midnight, the sheriff's office said in a statement. Responding deputies found the snow-covered road unpassable and hiked a half-mile in blizzard conditions to reach the woman's home.

The Clemons Fire Department brought in a tractor to clear a path for an ambulance. The woman gave birth at 12:38 a.m., and she and her baby were taken to Unity Point Health, authorities said.

Trump not worried about weather for Iowa Caucuses

In Des Moines, former President Donald Trump met with campaign volunteers on Sunday before heading to a rally in Indianola, less than 20 miles south. Trump is a heavy favorite to win the Republican Caucuses − a new Iowa Poll released Saturday night showed him leading the field by 28 percentage points.

This is expected to be the coldest Iowa Caucus ever. In 1972, the first Iowa Caucus, wind chills reached 26 degrees below zero. But the high temperature climbed to 25 degrees. Monday's expected high is minus 3 degrees.

"We seem to have a lot of good enthusiasm," Trump said. "I don't know, maybe the weather is not going to be that big a deal."

Dangerous road conditions are coming:We have tips for driving in snow.

West Coast not exempt from wintry weather, outages

Almost 170,000 homes and businesses were without power across Oregon early Sunday after a winter storm blasted across much of the state and Oregon and southwestern Washington. Temperatures dipped into the teens as power companies scrambled to bring back heat and light. Adding to the struggle: Strong winds with gusts above 80 mph tumbled trees and powerlines.

"As conditions remain hazardous for the next several days, we need you to stay home," Portland Mayor Ted Wheeler posted Saturday on social media. "As you are able, please check on your neighbors. It takes our entire community to get through this weather event."

Iowa won't be warming up soon

The high temperature in Des Moines was only expected to reach minus 9 degrees, close to the all-time record of minus 14 in January 1912. Today's wind chill could reach minus 40.

The reprieve won't come right away, either. The overnight low Sunday night was forecast at minus 17. Highs on Monday, Iowa Caucuses day and the Martin Luther King Jr. holiday, were expected to be minus 5 degrees. The temperatures will fall to minus 11 degrees Monday night, with a wind chill of minus 30, forecasters said.

"This extreme arctic air combined with breezy to strong winds will continue to create dangerous temperatures and wind chills through early next week, with wind chill values as low as 45 below zero possible at times," the weather service in Des Moines warned.

A 2007 study indicates poor weather benefits the Republican Party’s vote share − and may have contributed to presidential races in 1960 (good weather in several close states helped Democrat John F. Kennedy) and 2000 (rain in Florida helped Republican George W. Bush). But the caucuses are primaries and don't pit party against party.

Steelers vs. Bills:AFC wild-card game in Buffalo postponed until Monday due to weather

A different kind of 'delay of game' for Buffalo

In New York, the state Division of Homeland Security and Emergency Services urged Western New Yorkers to stay home.

"Travel in impacted areas will be impossible and dangerous at times throughout the weekend due to life-threatening blizzard-like conditions," the agency said in a statment.

Gov. Kathy Hochul cut a deal with the NFL to postpone Sunday's playoff game between the Buffalo Bills and the Pittsburgh Steelers. from Sunday to Monday.

"I've been in communication with @NFL commissioner Roger Goodell regarding the dangerous conditions in Buffalo this weekend," she wrote on social media. "In consultation with our emergency response teams, @BuffaloBills leadership, and the NFL, the Bills game will be postponed to 4:30 pm Monday."

Contributing: Marina Pitofsky, USA TODAY; Victoria Reyna-Rodriguez, José Mendiola and Philip Joens, the Des Moines Register