A massive winter storm dumped sleet, freezing rain and snow across much of the U.S. on Sunday, bringing subzero temperatures and halting air and road traffic. Tree branches and power lines snapped under the weight of ice, and hundreds of thousands of homes and businesses in the Southeast were left without electricity.

The ice and snowfall were expected to continue into Monday followed by very low temperatures which could cause “dangerous travel and infrastructure impacts” for days, the National Weather Service said.

Heavy snow was falling from the Ohio Valley to the Northeast, while “catastrophic ice accumulation” threatened from the Lower Mississippi Valley to the Mid-Atlantic and Southeast.

“It is a unique storm in the sense that it is so widespread,” weather service meteorologist Allison Santorelli said in a phone interview. “It was affecting areas all the way from New Mexico, Texas, all the way into New England, so we’re talking like a 2,000-mile spread.”

President Donald Trump approved emergency declarations for at least a dozen states by Saturday. The Federal Emergency Management Agency had rescue teams and supplies in numerous states, Homeland Security Secretary Kristi Noem said.

In New York, communities near the Canadian border saw record-breaking subzero temperatures, with Watertown registering minus 34 degrees Fahrenheit (minus 37 degrees Celsius) and Copenhagen minus 49 F (minus 45 C), Gov. Kathy Hochul said.

Coping with the storm

Freezing rain that slickened roads and brought trees and branches down on roads and power lines were the main peril in the South. In Corinth, Mississippi, heavy machinery manufacturer Caterpillar told employees at its remanufacturing site to stay home Monday and Tuesday.

“May God have mercy on Corinth, MS! ... The sound of the trees snapping, exploding & falling through the night have been unnerving to say the least,” resident Kathy Ragan wrote on Facebook.

In Clarksdale, Mississippi, Sanford Johnson said enough snow and sleet fell that few motorists ventured out.

“I had to break it to my youngest daughter that the play date she scheduled likely won’t happen today. We have no plans on driving,” Johnson said.

It already was Mississippi's worst ice storm since 1994 with its biggest-ever deployment of ice-melting chemicals — 200,000 gallons (750,000 liters) — plus salt and sand on roads, Gov. Tate Reeves said at a news conference.

He urged people not to drive anywhere unless absolutely necessary. “Do please reach out to friends and family," Reeves added.

In Nashville, Tennessee, Jami Joe, 41, feared her electricity might not last as ice-heavy limbs from oak and pecan trees continued to crash around her house. “It’s only a matter of time if a limb strikes a power line,” she said.

Because of icy roads, Josh Martin figured he and his wife, Misti, were “locked in” for a while at their home on a steep hill in Columbia, Tennessee.

“Getting in and out of the neighborhood is not an option,” Martin said. “I can get down because gravity will take me, but I could not get back up.”

Elsewhere, deep snow — over a foot (30 centimeters) in a 1,300-mile (2,100-kilometer) swath from Arkansas to New England — halted traffic and canceled flights.

On Manhattan's Upper East Side, January Cotrel enjoyed the fresh snow on a block that always closes during snowstorms for residents to sled, throw snowballs and make snowmen.

“I pray for two feet every time we get a snowstorm. I want as much as we can get,” she said. “Let the city just shut down for a day and it’s beautiful, and then we can get back to life.”

Storm knocks out power and snarls flights

As of Sunday morning, about 213 million people were under some sort of winter weather warning, Santorelli said. Hundreds of thousands of customers were without power according to poweroutage.us, with Tennessee and Mississippi hit especially hard.

Some 12,000 flights were canceled Sunday and nearly 20,000 were delayed, according to the flight tracker flightaware.com. Airports in Philadelphia, Washington, Baltimore, North Carolina, New York and New Jersey were among those impacted.

Bitter cold makes things worse

The danger will continue after the ice and snow, Santorelli warned.

“Behind the storm it’s just going to get bitterly cold across basically the entirety of the eastern two-thirds of the nation, east of the Rockies,” she said. That means ice and snow won’t melt as fast, which could hinder efforts to restore power.

In New York City, Mayor Zohran Mamdani said at least five people who died were found outside as temperatures plunged Saturday, though the cause of their deaths remained under investigation. He urged people to stay inside and off the roads: “We want every single New Yorker to make it through this storm.”

Two men died of hypothermia related to the storm in Caddo Parish in Louisiana, according to the state health department.

Across the affected areas, schools and universities announced that classes would be canceled or held remotely Monday.

Recovery could take time

In Oxford, Mississippi, police appealed for residents to stay home. Utility crews were also pulled from their jobs during the overnight hours.

“Due to life-threatening conditions, Oxford Utilities has made the difficult decision to pull our crews off the road for the night,” the utility company posted on Facebook early Sunday. “Trees are actively snapping and falling around our linemen while they are in the bucket trucks."

Oxford city officials posted dramatic photos on social media of slick roads and ice-coated trees sagging or breaking under the added weight.

In Tennessee, emergency officials urged motorists to give crews space to treat roads as drivers have been crashing into them.

Icy roads also made travel dangerous in north Georgia, where the Cherokee County Sheriff’s office posted on Facebook, “You know it’s bad when Waffle House is closed!!!” along with a photo of a shuttered restaurant. Whether the chain’s restaurants are open — known as the Waffle House Index — has become an informal way to gauge the severity of weather disasters across the South.

More than 11,400 flights canceled Sunday as massive winter storm sweeps across US

NASHVILLE (AP) — A massive winter storm made for a brutal travel day Sunday, with widespread cancellations and delays at some of the nation's busiest airports.

Widespread snow, sleet and freezing rain threatened nearly 180 million people — more than half the U.S. population — in a path stretching from the southern Rocky Mountains to New England, the National Weather Service said Saturday night. After sweeping through the South, the storm moved into the Northeast Sunday, and was expected to dump about 1 to 2 feet (30 to 60 centimeters) of snow from Washington through New York and Boston.

More than 11,400 flights were canceled on Sunday, according to flight-tracking site FlightAware. Aviation analytics firm Cirium said that as of Sunday morning, the storm is the highest experienced cancellation event since the pandemic.

By Sunday afternoon, the majority of flights were canceled at busy airports in the Northeast and elsewhere. LaGuardia Airport in New York closed Sunday afternoon, according to the Federal Aviation Administration. The agency said on its website the busy Queens airport grounded flights until 8 p.m.

In Philadelphia, 94% of flights, 326 flights, were canceled. Ninety-one percent of flights, 436 flights, were canceled at LaGuardia Airport in New York. New York’s John F. Kennedy International Airport had 466 flights canceled, about 80% of flights, according to FlightAware.

Ronald Reagan Washington National Airport said on its website that all airlines had canceled departing flights for the day, about 421 flights.

Significant disruptions also hit major airport hubs in Dallas-Fort Worth, Charlotte, Philadelphia and Atlanta, home to the nation’s busiest airport.

Allan Lengel of Detroit planned to return Monday from Fort Lauderdale, Florida, where the temperature has been in the 80s. But he’s staying until Wednesday after Delta suggested he change his reservation because of the weather impact on flights.

“Can’t say I’m disappointed. Frankly, I had been thinking of returning later because of frigid weather,” Lengel, 71, said, referring to conditions in Michigan.

American Airlines had canceled over 1,790 flights for Sunday, about 55% of its scheduled flights for Sunday, according to FlightAware. Delta Air Lines reported over 1,470 cancellations and Southwest Airlines reported over 1,340 cancellations for the day, while United Airlines had about 1,016. JetBlue had more than 590 canceled flights, accounting for roughly 72% of its schedule for the day.

Vikrant Vaze, a Dartmouth professor specializing in commercial aviation logistics, said recovery from the storm cancellations and delays will take days if not longer. And even for travelers who aren't in areas that were directly affected by weather, cascading delays could still affect their travel plans.

“Because there are so many different airlines involved, I think it’s going to come down heavily to the individual airline's network structure, the extent of hit that each of them has had, and just the intrinsic capacity of the airlines to handle these massive disruptions,” he said.

My flight was canceled, now what?

If you’re already at the airport, get in line to speak to a customer service representative. If you’re still at home or at your hotel, call or go online to connect to your airline’s reservations staff. Either way, it helps to also research alternate flights while you wait to talk to an agent.

Most airlines will rebook you on a later flight for no additional charge, but it depends on the availability of open seats.

Can I get booked on another airline?

You can, but airlines aren’t required to put you on another carrier’s flight. Some airlines, including most of the biggest carriers, say they can put you on a partner airline, but even then, it can be a hit or miss.

Am I owed a refund?

If your flight was canceled and you no longer want to take the trip, or you’ve found another way to get to your destination, the airline is legally required to refund your money — even if you bought a non-refundable ticket. It doesn’t matter why the flight was canceled.

The airline might offer you a travel credit, but you are entitled to a full refund. You are also entitled to a refund of any bag fees, seat upgrades or other extras that you didn’t get to use.

Mavericks' flights grounded by winter storm as NBA postpones games in Memphis and Milwaukee

MEMPHIS, Tenn. (AP) — The NBA postponed games in Memphis and Milwaukee on Sunday because of a massive winter storm that is creating dangerous travel conditions across much of the U.S.

The Dallas Mavericks tried twice to fly to Milwaukee for their Sunday night game against the Bucks, but conditions didn't allow it. A decision to postpone was announced a few hours before tipoff. Food that had been prepared for the game was donated to shelters in the Milwaukee area.

Earlier Sunday, a game between the Denver Nuggets and Memphis Grizzlies was postponed about three hours before tipoff.

Reschedule dates were not announced.

The league also changed the start times for two games on Monday: Philadelphia 76ers at Charlotte Hornets will tip off at 3 p.m. ET instead of 7 p.m., and the Indiana Pacers at Atlanta Hawks at 1:30 p.m. instead of 7:30 p.m.

The Memphis area was experiencing a mixture of snow, sleet and freezing rain that began falling early Saturday morning and continued Sunday morning. South and east of Memphis, freezing rain collected on power lines and trees, causing widespread outages and blocked roads. Authorities had recommended people stay off the streets as the wintry mix and frigid temperatures caused a refreeze.

The Nuggets said they planned to fly out at some point Sunday, depending on the conditions at Memphis International Airport. They are scheduled to play at home Tuesday against the Detroit Pistons.

The Grizzlies are scheduled to be in Houston for a game against the Rockets on Monday.

An NBA G League game scheduled for Monday between the Memphis Hustle and Stockton Kings in Southaven, Mississippi, was postponed and rescheduled for Feb. 19.

At least two college women's basketball games were postponed: No. 17 Tennessee’s visit to No. 18 Mississippi on Monday and Tulane's visit to Memphis on Tuesday. Reschedule dates were not announced.

In men's basketball, a game featuring Tennessee at No. 21 Georgia was pushed back a day from Tuesday to Wednesday. Purdue Fort Wayne and IU Indianapolis, and Southern Illinois and Evansville had Sunday games postponed without make-up dates announced.

The schedule changes come after dozens of games were moved around earlier in the week in anticipation of the storm.

Separately, on Saturday, the NBA postponed a game between the Warriors and Timberwolves to “prioritize the safety and security of the Minneapolis community” after the fatal shooting of a man by a federal officer in a district located less than two miles away from where the Timberwolves play.