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image caption Runways at Nashville airport in Tennessee have had to be cleared of ice and snow
Authorities across the US are on alert as a winter storm brings freezing winds, ice and snow to many areas that rarely see such frigid conditions.
President Joe Biden has approved a state of emergency in Texas where a surge in demand for electricity has led to widespread power cuts.
The National Weather Service (NWS) said more than 150 million Americans were now under winter storm warnings.
Kentucky, Mississippi, Alabama, Oregon and Oklahoma are among states affected.
The freezing storm even reached northern parts of Mexico where more than four million homes and businesses lost power early on Monday.
Icy roads have led to a spate of traffic accidents. In Houston, Texas, nearly 120 road crashes were reported on Sunday alone. A pile-up on a major highway near Oklahoma City during a snowstorm on Sunday left several lorries on fire.
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Travellers in several states have also been warned that flights could be delayed or cancelled. In Houston, Texas, the George Bush Intercontinental Airport and the city’s Hobby Airport were both closed until at least Tuesday.
The NWS said unusual meteorological conditions had allowed an “Arctic outbreak” that originated just above the US-Canada border to spill out into and across the US.
“Over 150 million Americans are currently under winter storm warnings, ice storm warnings, winter storm watches, or winter weather advisories as impactful winter weather continues from coast to coast,” the NWS said in a statement.
“Hundreds of daily low maximum and minimum temperatures have been/will be broken during this prolonged ‘polar plunge,’ with some February and even all-time low temperature records in jeopardy.”
Up to 12in (30cm) of snow are expected across parts of the southern Plains – the large area that spans parts of Texas, Oklahoma and Kansas – according to NWS meteorologist Marc Chenard.
“Typically, we just don’t have quite this much cold air in place that far south,” he said.
In Louisiana, some local authorities have imposed curfews to keep people off the icy roads. The state is also suffering power cuts and traffic disruption.
Texas has seen some of its coldest temperatures in more than 30 years and some areas on Sunday hit 0F (-18C). Temperatures in the city of Dallas have been colder than in Anchorage, Alaska, CBS News reported.
Texas Governor Gregg Abbott, who declared a state of emergency on Sunday, urged “all Texans to remain vigilant against the extremely harsh weather”.
Rotating power cuts were initiated by the state’s power grid operator, the Electric Reliability Council of Texas (Ercot), early on Monday, to reduce demand on the electricity system.
The crisis was worsened when nearly half the state’s wind power generation was knocked out by the storm on Sunday. Wind power is the state’s second-largest source of electricity.
The website PowerOutage.us said more than 2.8 million customers in Texas were suffering power cuts on Monday afternoon.
Ercot also issued a level-three energy emergency alert, urging consumers to reduce electricity use.