Washington (AFP) -
Millions were left without power as a winter storm gripped the southern and central United States Tuesday with record-low temperatures in ill-prepared areas, and a tornado claiming three lives.
More than 20 storm-related deaths have been registered so far, including in traffic accidents in Texas, Kentucky and Missouri, according to local media.
In hardest-hit Texas -- where freezing conditions prompted utility companies to implement rotating blackouts -- a woman and girl died from carbon monoxide poisoning after using a car to generate heat, according to NBC News.
In Houston on Monday, a homeless man was killed 'possibly from exposure,' according to the Harris County Sheriff's Department, and the city's police chief said another man had been found dead after potential exposure to low temperatures.
A man in Louisiana died when he hit his head after slipping on ice, and a 10-year-old Tennessee boy died after he and his six-year-old sister fell through the ice into a pond Sunday.
President Joe Biden on Tuesday vowed to provide additional emergency resources for those affected by the 'historic storm.'
He also thanked 'road workers, highway patrol officers, and first responders who are taking swift action in horrific conditions to save lives,' according to a White House statement.
The winter storm spawned at least four tornadoes, according to Atlanta-based weather.com, including one in coastal North Carolina late Monday that killed at least three people and injured 10 more.
'It is estimated that at least 50 homes were affected in the incident and several power lines were damaged, causing power outages,' Brunswick County Emergency Services said in a statement.
Photos and video broadcast by US media showed downed trees, flattened homes and smashed cars.
According to the Poweroutage.us tracking site, more than three million residential, commercial and industrial customers were without electricity in Texas as of Tuesday evening.
- Plow shortage -
In the state capital Austin, the temperature dropped to 10 degrees Fahrenheit (-12 degrees Celsius) -- well below February's average low of 45F. By contrast, thermometers in Anchorage, Alaska read 20F.
Rare wintry scenes played out in Houston, where locals built snowmen and sledded.
'It's lovely to see the white but very dangerous at the same time because people here don't know how to drive in it,' Houston resident Michael, who only gave his first name, told AFP.
'You know they're driving too fast.'
In Mississippi, residents woke up to discover much of the Deep South state transformed into a snow-and-ice-covered landscape.
Authorities were reportedly struggling to clear roads, as they did not have snow plows because the state so rarely needs them.
Officials across the US urged residents to exercise caution in navigating the perilous conditions.
Weather-related emergencies have been declared in Texas, Alabama, Oklahoma, Kansas, Mississippi and Oregon -- where nearly 200,000 customers were without power.
The National Weather Service (NWS) said the winter storm will move towards the northeast US before 'making a beeline for eastern Canada.'
'But not before it causes heavy snow and freezing rain in parts of the eastern Great Lakes and New England,' the NWS said.
New York governor Andrew Cuomo on Monday ordered emergency services to prepare for sleet, ice and freezing rain.
'This massive weather system is making its way across the country and ready to deliver a one-two punch of snow, ice and heavy winds across the entire state for the next two days,' he said in a statement.
Further inland, Chicago was expecting to see up to 14 inches of snow before the end of the cold snap. The weather had caused almost 60 flight cancelations at local airports by Tuesday morning, the local ABC affiliate reported.