Schools and roads were shut nationwide and flights cancelled as “life-threatening” conditions spread from Texas to New England, the National Weather Service said, News.Az reports, citing BBC.
At least two deaths were attributed to hypothermia in Louisiana, while additional fatalities linked to the storm were reported in Texas, Tennessee and Kansas.
By Sunday afternoon, more than 800,000 households were without electricity, according to PowerOutage.us. Flight tracking service FlightAware reported that over 11,000 flights had been cancelled as the severe weather disrupted travel across the country.
Widespread heavy snow, sleet and freezing rain, which is a dangerous phenomenon where cooled rain droplets freeze instantly on surfaces, could last for days, and the storm could affect around 180 million Americans - more than half the population.
"The snow and the ice will be very, very slow to melt and won't be going away anytime soon, and that's going to hinder any recovery efforts," Allison Santorelli, a meteorologist with the National Weather Service, told the BBC's US media partner CBS News.
Louisiana's Department of Health confirmed on Sunday that two men had died of hypothermia.
The mayor of Austin, Texas, said there had been an "exposure-related" death.
Officials in Kansas said a woman, whose body was found on Sunday afternoon covered in snow, "may have succumbed to hypothermia".
Weather-related deaths of three people have also been reported in Tennessee.
New York City Mayor Zohran Mamdani wrote in a post on X that at least five people in the city had died on Saturday but added their cause of death was yet to be determined.
He said, however, "It is a reminder that every year New Yorkers succumb to the cold".
New York state Governor Kathy Hochul warned residents to stay inside and off roads.
"This is certainly the coldest weather we've seen, the coldest winter storm we've seen in years," she said on Sunday.
"A sort of an arctic siege has taken over our state and many other states across the nation."
Hochul said the "brutal" conditions were expected to bring the longest cold stretch and highest snow falls in years.
"It is bone chilling and it is dangerous," she said.
Kentucky Governor Andy Beshear said on Sunday that the state was seeing more ice and less snow than was originally predicted.
"That is not good news for Kentucky," he said.
Weather experts have warned that one of the biggest dangers of the storm is ice, which has the potential to damage trees, down power lines and make roads unsafe.
In Virginia and Kentucky, authorities have responded to hundreds of crashes on roads.
Canadians have also been hit with heavy snow and hundreds of cancelled flights.
Officials estimate that there will be 15-30cm (5-11in) of snowfall in the province of Ontario.
Nearly half the states have declared emergencies, and schools across the country are already canceling classes in anticipation of the storm continuing into Monday. The US Senate has also scrapped a scheduled vote for Monday evening.
In declaring an emergency in the nation's capital, Washington Mayor Muriel Bowser said: "We're experiencing the biggest snowstorm in a decade in DC this weekend."
While places in the north such as the Dakotas and Minnesota are used to below- freezing temperatures in winter, it is unusual to see such extreme cold in states like Texas, Louisiana and Tennessee, where temperatures are around 15-20C below the seasonal average.
Those states could also see ice accretions of around an inch caused by freezing rain.
