A huge winter storm sweeping across the southern US has killed at least 21 people and left millions without power.
There have been widespread blackouts in Texas, where the energy grid was overwhelmed by a surge in demand, reports BBC.
Millions of people in the state, which rarely experiences such low temperatures, have been struggling to cope with the lack of power and frigid conditions.
The extreme weather is forecast to continue until the weekend.
Deaths attributed to the storm have been recorded in Texas, Louisiana, Kentucky, North Carolina and Missouri.
How long will the storm last?
By Wednesday afternoon, the National Weather Service (NWS) said that the worst of the storm had moved through Texas, but kept more than 100 million Americans under a winter weather warning.
But historically low temperatures are expected to remain for days, the NWS said, with more than 71% of the US covered by snow.
The freezing storm has even reached northern and central parts of Mexico, where millions of people have experienced days of intermittent power cuts.
"I'm in Houston, Texas freezing to death," one Twitter user, Chris Prince, wrote. "No power, no heat, no water. I have four young children. How is this happening right now?"
Another user, Josh Morgerman, wrote that a friend in Texas had resorted to "burning furniture in the fireplace" to stay warm.
Texas family 'trying to keep warm'
A senior director for Ercot - the Electric Reliability Council of Texas - told CNN on Wednesday that Texans could continue to experience rotating power outages into Thursday.
Rotating outages are the "best case" scenario, Dan Woodfin said. "I don't think it's likely that we're going to have enough available based on our forecasts... and that we're going to have everybody back on today, or before at least the morning peak tomorrow".
Scientists have linked climate change to an increasing number of severe weather events worldwide, including hurricanes, heat waves and floods.
'Public health disaster'
The recorded deaths include people who have died in traffic accidents, as well as some who suffered carbon monoxide poisoning from running cars and generators indoors to stay warm.
"This is an absolute public health disaster," one medical official in Houston told the local television station KPRC-TV. "[Carbon monoxide poisoning] certainly happens when it gets cold, but never in these numbers.
Queues have formed at shops in Texas where many are unused to freezing temperatures
One county said it had seen more than 300 suspected carbon monoxide cases during the cold snap. "It's turning into a mini mass casualty event," one Harris County doctor told the Houston Chronicle.
At least four people were killed following a house fire in Houston that officials said may have been sparked by candles. Separately, police said two men found alongside a Houston highway were believed to have died due to the cold.