Wind farms in West Texas, stricken by weekend ice storms, were particularly hard hit.
Responding to a request from Governor Greg Abbott, President Joe Biden granted a federal emergency declaration for all 254 counties in the state on Sunday, authorising U.S. agencies to coordinate disaster relief from severe weather in Texas.
As such, over 320,000 power outages were reported across OR with Portland General Electric reporting the majority of power outages, affecting 280,000 customers as of Monday at noon and Pacific Power reporting the second highest number of outages with 40,000 affected customers.
Icy roads have led to a spate of traffic accidents. In Houston, Texas, almost 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.
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.
As of Monday morning, more than 150 million Americans were under winter weather advisories, some of which extend well into Tuesday.
There will be historic record-breaking cold on Monday night that will occur from the Plains down to Texas and into Alabama where these temperatures have not been seen for decades. The Dallas Morning News reports that areas northwest of the city could see as much as 10 inches of accumulation.
President Joe Biden granted a federal emergency declaration for all 254 counties in the state on Sunday.
The state of Texas continued to reel under a deep freeze, leaving utilities scrambling to meet record power demand and forcing the state's grid operator to enforce rotating blackouts early on Monday.
With these two storms affecting most of the lower 48 states, a lot of ice and snow is expected to fall this week from Washington to Texas and up to Maine. Wind generation ranks as the second-largest source of electricity in Texas, accounting for 23% of state power supplies, ERCOT estimates.
As of 8 a.m. ET Monday, more than 2 million customers in Texas and about 25,000 in Louisiana had no electricity.