Almost 30in (76cm) of snow fell in California over a 24-hour period ending Sunday morning, causing road closures, including a 70-mile (112km) stretch of Interstate 80 into Nevada.
Avalanche warnings are in effect across six states.
Over the weekend, southern California was hit by rainstorms, which saw power lines snap and streets flooded.
More than 1.8in of rain fell over 24 hours in San Marcos pass in Santa Barbara county, while Rocky Butte in San Luis Obispo county recorded 1.61in, officials said.
The National Weather Service (NWS) in Reno, Nevada, said snowstorms would remain heavy well into Monday, and forecasters have warned that travel could prove difficult in the region for several days.
Avalanche warnings were put into effect on Sunday for parts of Nevada, Utah, Idaho, Montana, Colorado and California, as the storms created widespread areas of unstable snow. The NWS issued a winter storm warning for greater Lake Tahoe into Tuesday.
Power cuts affected residents in Washington, Oregon and other areas, although northern California was the worst hit. Power Outage US reported 56,000 power cuts there in the early hours of Monday local time, mostly in northern coastal counties and those on the Nevada border.
In Montana, the NWS warned that "dangerously cold wind chills could cause frostbite on exposed skin in as little as five minutes". Wind chill could make the temperatures feel as low as -48C.
One benefit of the storms in California will be to replenish the Sierra snowpack. It accounts for about 30% of California's fresh water supply and had been at dangerously low levels after weeks of dry weather.
The state's department of water resources reported on Christmas Eve that the snowpack was between 114% and 137% of normal ranges, with more snow expected.
While the west coast is battered by heavy storms, many southern states have been experiencing "unusually warm temperatures", with dozens of cities on track for their warmest December on record.
The NWS reported that Wichita Falls, near Texas's border with Oklahoma, had reported a record temperature of 32C (90F), while Houston saw temperatures hit 27C.