More than two million people in Texas have been left without electricity as snowstorms and freezing temperatures hit parts of the US.
Demand for power in Texas forced the electric grid operator to impose rotating outages.
US President Joe Biden declared a federal emergency in the state, where temperatures fell as low as -22C (-7.6F).
Average temperatures in central and southern Texas during February usually hover between 20C and 24C (68F and 75F).
The spot price of wholesale electricity on the Texas power grid has risen more than 10,000% amid the deep freeze.
Real-time wholesale market prices on the power grid operated by the Electric Reliability Council of Texas (ERCOT) have climbed as high as $11,000 per megawatt.
A typical price on the grid, which supplies most of the electricity for the state, is less than $100 per megawatt.
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Also, oil refineries have been closed and restrictions placed on operators of natural gas pipelines due to the severe weather.
Dallas saw up to six inches (0.5ft) of snow.
Houston’s George Bush Intercontinental Airport said its airfield would remain closed until 1pm (7pm GMT) and Hobby Airport will cease operations until at least Tuesday.
Texas Governor Greg Abbott warned that “every part of Texas” would face freezing conditions and that, while transport workers were trying to make travel as safe as possible, “what becomes frozen will remain frozen for a long period of time”.
There were nearly 120 crashes on Houston’s icy roads during Sunday.
NBC meteorologist Janessa Webb said Monday saw more than 60 records set for low temperatures and that a similar situation was expected on Tuesday in the central states.
“Records could be smashed by a couple of degrees, which is impressive for lows,” she added.
“There will be a slow improvement in the cold Wednesday through Friday.
“The cold is really concentrated in the middle of the country, with the coasts being no more than 5 to 10 degrees below average.”
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An Arctic air mass has settled over much of the country, from the Pacific Northwest through to the Great Plains and into the mid-Atlantic states.
The storm system in the Southern Plains has been travelling up the Northeast, bringing heavy snow and freezing temperatures to Washington, Oregon and Idaho, the National Weather Service said.
In Louisiana, where freezing temperatures also cut power and closed roads, some parishes were implementing curfews to keep residents off the road.
Severe winter weather warnings covered more than 2,000 miles – 26 states and 150 million Americans.