More than 95 million people in the United States were under a wind chill warning or advisory on Sunday as an “Arctic blast” enveloped huge parts of the country, while the South was expected to get snow and the Northeast braced for blinding wind-driven squalls, forecasters said.

The National Weather Service reported wind chill readings on Sunday of 19 degrees below zero in Arkansas, 9 degrees below zero in Dallas and 60 degrees below zero in Montana. Low temperatures are expected to grip most of the country through the middle of the week.

“These wind chills will pose a risk of frostbite on exposed skin and hypothermia,” the Weather Service said. “Have a cold survival kit if you must travel.”

The extreme weather has proved to be dangerous in other ways. Strong winds knocked a tree onto a home in northwest Lake Oswego, Ore., on Saturday morning, killing a man inside, said Sgt. Tom Harper, of the Lake Oswego Police Department. More than 100 trees fell in the area over the weekend, he said.

Also in Oregon, Portland Fire and Rescue struggled to reach the scene of an R.V. fire in the southeast part of the city because of road closures from fallen power lines and trees. The emergency vehicles had to move slowly because of slick roads, said Lt. Terry Foster, the fire inspector.

An open-flame stove was being used to heat the R.V., and a tree fell on it, starting the fire. One woman in her early 30s was killed, while three other people in the recreational vehicle managed to escape.

As of Sunday afternoon, Oregon was experiencing widespread power outages, with about 162,000 customers without power. Pennsylvania had the second-highest number of outages, with 88,000 customers without power, according to Poweroutage.us.

High temperatures on Sunday and Monday will likely be 20 to 40 degrees below average from Montana to Texas.

Potential snow squalls — bursts of snow accompanied with strong winds — will spread east-northeastward Sunday across Pennsylvania into parts of southern New York and possibly into New York City.

A wind advisory posted on Sunday includes the Philadelphia metropolitan area and points east to the northern New Jersey coast. Winds gusting to 40 to 50 miles per hour can lead to whiteout conditions for 15 to 20 minutes.

The powerful winds could damage trees and lead to power failures, the Weather Service said.

Lake-effect snow is also a threat this weekend in the Great Lakes region, with the potential for whiteouts in Michigan, Wisconsin and western and northern New York State.

Multiple winter storm warnings were in effect Sunday morning around the Buffalo region, where up to two feet of snow were predicted to fall throughout the weekend. Gov. Kathy Hochul of New York warned residents on Friday to take shelter ahead of this weekend’s storm and to prepare for power failures.

Because of the weather, the N.F.L.’s wild card weekend game between the Pittsburgh Steelers and the Buffalo Bills at Highmark Stadium in Orchard Park, N.Y., was postponed to Monday at 4:30 p.m. Eastern time from Sunday at 1 p.m.

Around New York and northeastern Pennsylvania, the Weather Service forecast snow and localized wind gusts of up to 50 m.p.h. New York City could get an inch to two inches of snow Monday night into Tuesday.

Arkansas and Tennessee could receive up to six inches of snow.

Snow, sleet, rain and dangerous wind chills are expected to batter the West Coast, the Plains, parts of the Northeast and to extend into sections of the South.

Snow and freezing rain is expected from the West Coast to the Rocky Mountains. The heavy snow and ice have the makings for “poor to impossible” travel conditions in Idaho, Nevada, Oregon and Utah.

Moving east from the Northern Rockies to northern Kansas and Iowa, wind chills will drop below minus 30 degrees, forecasters said, adding that dangerously cold weather “will persist and redevelop” over parts of the Midwest.

Parts of the South will experience cold weather as “wintry precipitation,” including snow, sleet and freezing rain, are forecast to develop across several states. Ice is also expected for parts of central Texas through the lower Mississippi Valley.

The Electric Reliability Council of Texas, known as ERCOT, issued a weather watch, though it stated on social media that the state’s electrical “grid conditions are expected to be normal.”

Judson Jones contributed reporting.