Nearly 170 million people are under winter weather advisories Monday, with icy roads, power outages, and dangerously low temperatures threatening to snarl traffic and paralyze cities from coast to coast.
The severe winter weather has sparked emergency declarations in at least seven states, including Alabama, Oregon, Oklahoma, Kansas, Kentucky, Mississippi and Texas — which has borne the brunt of the cold weather.
Officials in Harris County, Texas, warned residents during a press conference Sunday night to stay indoors.
"The window to prepare for this historic storm has closed as the time to hunker down is here," Harris County Judge Lina Hidalgo said, adding that the dual threat of ice on the ground and extreme cold weather is going to pose "serious challenges."
The Houston area has been hit especially hard. Both airports are closed and city police responded to more than 130 traffic accidents Sunday night, Police Chief Art Acevedo said in a tweet.
A 10-car pileup on Interstate 45, south of downtown, was just one of many incidents on icy roads.
"Please avoid traveling until this severe weather event subsides," Acevedo said.
Houston Mayor Sylvester Turner, who declared a state of emergency earlier in the day, echoed the chief's orders.
"Please stay off the roads tonight and through tomorrow. This is serious! The roads are dangerous!"