A winter storm sent mercury plunging across the Southern Plains, prompting a power emergency in Texas a day after flights were cancelled and traffic affected across large parts of the US.
Rotating power cuts were initiated by the Electric Reliability Council of Texas, or Ercot, early on Monday morning.
Thousands went without electricity for short periods as the temperature fell below 0°C near Dallas and Houston.
“We urge Texans to put safety first,” Ercot, which manages the flow of electricity in the state, said on Twitter as it urged residents to use less energy.
“Traffic lights and other infrastructure may be temporarily without power,” it said.
The council described the rotating cuts as a “last resort to preserve the reliability of the electric system as a whole”.
It said utility companies would determine how to reduce demand on the system.
“Every grid operator and every electric company is fighting to restore power right now,” said Ercot president and chief executive Bill Magness.
The rotating cuts were expected to last throughout Monday morning.
More than 1.6 million customers were in the dark as of 5am local time, said poweroutage.us, a utility tracking site.
About 5,000 Oklahoma Gas and Electric customers were without power overnight, and Entergy Arkansas logged about 3,000 cuts. Both states have much smaller populations than Texas.
Officials in Houston warned people to prepare for cuts and dangerous roads in conditions similar to what residents might experience after a Category-5 hurricane.
“There have been numerous reports of accidents from icing recently,” National Weather Service lead forecaster Bob Oravec said on Monday.
“I think there’s going to be a big threat today as the system pushes north-eastward.”
Up to 30 centimetres of snow was expected across parts of the Southern Plains into Monday, said Marc Chenard, a forecaster with the weather bureau.
The region was preparing for the winter weather for most of the weekend.
Texas Governor Greg Abbott issued a disaster declaration for all 254 of the state’s counties.
Mr Abbott, Oklahoma Governor Kevin Stitt and Arkansas Governor Asa Hutchinson activated National Guard units to assist state agencies with tasks including rescuing stranded drivers.
US President Joe Biden also declared an emergency in Texas in a statement on Sunday night.
The declaration is intended to add federal aid to state and local responses.
More than 760 flights were cancelled at Dallas-Fort Worth International Airport, and at Dallas Love Field most of the nearly 200 flights for Southwest Airlines, the airport’s main carrier, were cancelled on Sunday.
American Airlines said about 345 of its flights through DFW Airport, its base, were cancelled by early Sunday afternoon.
The airline said the storm was also affecting its flights across the region, with operations reduced and cancelled at airports in Texas, Oklahoma and Arkansas.
