Massive US storm leaves 20 dead, millions without power

City worker Kaleb Love breaks ice on a frozen fountain in Richardson, Texas. Photo / AP

A US storm that left millions without power in record-breaking cold weather has so far claimed 20 lives.

The storm that overwhelmed power grids and immobilised the Southern Plains carried heavy snow and freezing rain into New England and the Deep South and left behind painfully low temperatures. Wind-chill warnings extended from Canada into Mexico.

In all, at least 20 deaths were reported. The weather also threatened to affect the nation's Covid-19 vaccination effort. US President Joe Biden's administration said delays in vaccine shipments and deliveries were likely.

North Carolina's Brunswick County had little notice of the dangerous weather, and a tornado warning was not issued until the storm was already on the ground.

A homeless person at the Chicago Transit Authority's Dearborn bus station. Photo / AP

The National Weather Service was "very surprised how rapidly this storm intensified ... and at the time of night when most people are at home and in bed, it creates a very dangerous situation", Emergency Services Director Ed Conrow said.

In Chicago, 46cm of new snow forced public schools to cancel in-person classes today. Hours earlier, along the normally balmy Gulf of Mexico, cross-country skiier Sam Fagg hit fresh powder on the beach in Galveston, Texas.

The worst power outages were in Texas, affecting more than two million homes and businesses. More than 250,000 people also lost power across parts of Appalachia, and another 200,000 were without electricity following an ice storm in northwest Oregon, according to poweroutage.us, which tracks utility outage reports.

Four million people lost power in Mexico.

Texas officials requested 60 generators from the Federal Emergency Management Agency and planned to prioritise hospitals and nursing homes. The state opened 35 shelters to more than 1000 occupants, the agency said.

More than 500 people sought comfort at one Houston shelter. Mayor Sylvester Turner said other warming centres were closed because they lost power.

After losing power on Monday (Tuesday NZT), Natalie Harrell said she, her boyfriend and four kids sheltered at a Gallery Furniture store in Houston. The warming centre at the store provided people with food, water and power to charge essential electronics.

"It's worse than a hurricane," Harrell said. "I think we are going to be more days without light, that is what it seems like."

Utilities from Minnesota to Texas implemented rolling blackouts to ease the burden on power grids straining to meet extreme demand for heat and electricity.

Blackouts lasting more than an hour began around dawn on Tuesday for Oklahoma City and more than a dozen other communities, stopping electric-powered space heaters, furnaces and lights just as temperatures hovered around minus 22 degrees Celsius.

Oklahoma Gas & Electric rescinded plans for more blackouts but urged users to set thermostats at 20C, avoid using major electric appliances and turn off lights or appliances not in use.

Nebraska's blackouts came amid some of the coldest weather on record: in Omaha, the temperature bottomed out at minus 30C, the coldest in 25 years.

The Southwest Power Pool, a group of utilities covering 14 states, said the blackouts were "a last resort to preserve the reliability of the electric system as a whole".

People queue for groceries in Austin, Texas. Photo / AP

The outages forced a Texas county to scramble to administer more than 8000 doses of Moderna's coronavirus vaccine after a public health facility lost power and its backup generator also failed.

County officials distributed the doses that could have spoiled at three hospitals, Rice University and the county jail.

Texas officials said more than 400,000 doses due now will not arrive until at least Wednesday because of the storm.

The tornado that hit North Carolina's Brunswick County was an EF3 with winds estimated at 257km/h, the weather service said on Twitter.

Three people died and 10 were injured when the tornado tore through a golf course community and another rural area just before midnight Monday, destroying dozens of homes.

Authorities in multiple states reported deaths in crashes on icy roads, including two people whose vehicle slid off a road and overturned in a waterway in Kentucky on Sunday.

In Texas, three young children and their grandmother died in the Houston-area fire, which likely began while they were using a fireplace to keep warm during a power outage, a fire official said. And in Oregon, authorities on Tuesday confirmed the deaths four people last weekend in the Portland metro area of carbon monoxide poisoning.

At least 13 children were treated for carbon monoxide poisoning at Cook Children's Medical Centre in Fort Worth, the hospital said in a social media post, which warned that families were "going to extreme measures to warm their homes" — with propane or diesel-burning engines and generators, gas ovens and stovetops. One parent died of the toxic fumes, paediatrician Phillip Scott told Fort Worth television station KTVT.

Several cities had record lows: in Minnesota, the Hibbing/Chisholm weather station registered minus 39C; Sioux Falls, South Dakota, dropped to minus 26C.

At midday, more than 2700 US flights had been cancelled.

Authorities pleaded with residents to stay home today. About 100 school systems closed, delayed opening or switched to remote classes in Alabama, where forecasters said conditions might not improve until temperatures rise above freezing on Wednesday afternoon.