A massive winter storm sweeping across large parts of the United States has killed at least 10 people, grounding flights, knocking out power and prompting warnings to stay off the roads as freezing conditions dragged into Monday.
The system dumped snow, sleet and freezing rain across a wide swath of the country, with officials warning that an Arctic air mass trailing the storm would drive temperatures to dangerously low levels for days, prolonging disruptions to daily life.
The National Weather Service said little relief was expected through Monday morning and urged residents to brace for continued hazardous conditions.
In New York, Mayor Zohran Mamdani said five people were found dead outdoors over the weekend amid the extreme cold. While the deaths were not officially confirmed as weather-related, Mamdani called the situation "a powerful reminder of the danger of extreme cold.”
Texas authorities confirmed three storm-related deaths, including a 16-year-old girl killed in a sledding accident.
Two people died of hypothermia in Louisiana, the state health department said.
The PowerOutage.com tracking site showed more than 840,000 customers without electricity as of Sunday night, mostly in the South, where the storm intensified Saturday.
In Tennessee, where a band of ice downed power lines, more than 300,000 residential and commercial customers were without electricity. Louisiana, Mississippi and Georgia, states less accustomed to such storms, each reported more than 100,000 outages.
The outages are particularly dangerous as the South is being battered by treacherous cold that the NWS warned could set records.
Authorities from Texas to North Carolina and New York urged residents to stay home because of perilous conditions.
"Stay off the roads unless absolutely necessary,” the Texas Division of Emergency Management posted on X.
The storm moved into the Northeast on Sunday, dumping snow and sleet on heavily populated cities including Philadelphia, New York and Boston.
At least 20 states and Washington, D.C., declared states of emergency.
Residents in the nation’s capital awoke to several inches of snow on sidewalks and roads, followed by heavy sleet. Federal offices were preemptively closed Monday.
Several major airports in Washington, Philadelphia and New York reported nearly all flights canceled for the day. Tracking site FlightAware showed more than 19,000 flights into and out of the country had been canceled since Saturday.
President Donald Trump, who remained at the White House during the storm, wrote on his Truth Social platform Saturday: "We will continue to monitor and stay in touch with all states in the path of this storm. Stay safe, and stay warm!”
Polar vortex
The brutal storm system is the result of a stretched polar vortex, a region of cold, low-pressure air near the Arctic that typically forms a compact, circular system but can distort, sending frigid air spilling across North America.
Scientists say the increasing frequency of such disruptions may be linked to climate change, though the issue remains debated and natural variability plays a role.
Trump, who has questioned climate change science and rolled back green energy policies, raised doubts about how the cold fit into broader climate trends.
"WHATEVER HAPPENED TO GLOBAL WARMING???” he posted.
The NWS warned heavy ice could cause "long-duration power outages, extensive tree damage, and extremely dangerous or impassable travel conditions,” particularly in states less accustomed to severe winter weather.
Forecasters also warned of life-threatening cold lasting up to a week after the storm, especially in the Northern Plains and Upper Midwest, where wind chills were expected to plunge below minus 45 degrees Celsius (minus 50 degrees Fahrenheit).
Such temperatures can cause frostbite within minutes.