Bitter temperatures and biting winds had much of the northeastern United States bundling up for some of the worst cold of the winter.
The snap was so bad it forced the cancellation of an ice festival in New York's Central Park and caused an interstate highway pile-up in Pennsylvania that killed at least three people.
"These temperatures can be life threatening - especially for seniors, infants and people with medical conditions," New York City Mayor Bill de Blasio said.
Stay indoors and take care of each other, he counselled.
Police said weather was a factor in a deadly pile-up in Pennsylvania that saw dozens of vehicles - tractor-trailers, box trucks, cars and SUVs - tangled together across three lanes and the snow-covered median of Interstate 78. A snow squall appears to have moved through at the time of the crash.
The bone-chilling cold cancelled horse racing at Hollywood Casino at Charles Town Races in West Virginia and at New York's Aqueduct Racetrack. The Central Park Ice Festival, which was to feature ice-carving artists and music, was also shelved.
A wind chill advisory was in effect for New York City through noon on Sunday. With the actual temperatures falling as low as minus 20C, the weather service says the city could see wind chills of minus 28C to minus 31C. Wind gusts may reach 72km/h.
City department of homeless services officials were on the streets responding to reports of people in need of shelter. On Friday night, 62 people were brought into shelters and 207 people came to hospitals to get out of the cold.
Subzero temperatures were also expected in the Boston area.
Though the temperatures were frigid, they weren't necessarily record-setting. The record for cold in Concord, New Hampshire, on Valentine's Day is minus 33C, and Sunday's forecast is for a low of minus 23.5C, said meteorologist Bob Marine.
Meanwhile, in the West, heat records have fallen in recent days, from Oregon to Los Angeles, where surfers hit the beaches and golfers strolled fairways.
Much of California marked its 10th straight day on Friday without measurable precipitation and temperatures reached 35C.
The blue skies were increasingly unwelcome in a state that just logged its four driest years on record.
