The death toll on Tuesday included three people found dead after a tornado hit a seaside town in North Carolina and four family members who perished in a Houston-area house fire while using a fireplace to stay warm..
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.
Among the 20 deaths reported were those from car crashes and carbon monoxide poisoning.
The weather also threatened to affect the nation’s COVID-19 vaccination effort. President Joe Biden’s administration said delays in vaccine shipments and deliveries were likely.
Power outages occurred across in Texas, affecting more than two million homes and businesses, and another 200,000 were without electricity following an ice storm in northwest Oregon. Four million people lost power in Mexico.
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 early Monday and its backup generator also failed.
Texas officials said more than 400,000 doses due now will not arrive until at least Wednesday because of the storm.
A tornado that hit North Carolina’s Brunswick County packed winds estimated at 260km/h.
Three people died and 10 were injured when the tornado tore through a golf course community and another rural area just on 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.
A Mississippi man died after losing control of his vehicle, which overturned on an icy road.
In Texas, three young children and their grandmother died in a Houston-area fire, which likely began while they were using a fireplace to keep warm during a power outage.
And in Oregon, authorities on Tuesday confirmed the deaths four people last weekend in the Portland metro area of carbon monoxide poisoning.
Other Texas deaths included a woman and a girl who died from suspected carbon monoxide poisoning in Houston at a home without electricity from a car left running in an attached garage, and two men found along Houston-area roadways who likely died in sub-freezing temperatures, law enforcement officials said.
In western Tennessee, a 10-year-old boy died after falling into an ice-covered pond on Sunday during a winter storm, fire officials said.
Several cities had record lows including Hibbing, Minnesota at minus 39C and Sioux Falls, South Dakota at minus 26C.
At midday on Tuesday, more than 2700 US flights had been cancelled.
Authorities pleaded with residents to stay home.