SEATTLE — A thaw-out is coming for frozen Seattle and Portland, Oregon, but not before another round of snow that could compound problems for a region more accustomed to winter rain than arctic blasts.

More snow and rain fell on California on Wednesday, causing travel disruptions on mountain routes and raising the risk of debris flows from wildfire burn scars.

And in Nevada the governor plans to declare a state of emergency due to snow and storm conditions affecting travel in the Lake Tahoe area of northern Nevada.

Forecasters say parts of western Washington could see up to 3 inches (7.6 centimeters) of snow Thursday and northwestern Oregon could see a similar amount.

The normally temperate part of the Pacific Northwest has shivered with temperatures hitting the single digits in some areas this week after extreme cold air from Canada’s Fraser River Valley blew in on Sunday.

Snow and ice has made travel treacherous in some parts, forced closures and travel delays and prompted people to take shelter in emergency warming centers.

The weather and the pandemic have forced the cancellation of nearly 1,300 flights into and out of Seattle-Tacoma International Airport since Sunday. The situation has been acute in Alaska, where hundreds of passengers, many from coastal villages, have been stranded in the town of Bethel because of bad weather and ill-equipped airports.

Temperatures could rise above freezing in Seattle Thursday and be even warmer in Portland, before airflow from the Pacific blows in on the weekend and causes the mercury to rise to more seasonable highs in the 40s Fahrenheit (4.4 Celsius).

State officials in Oregon have declared an emergency. In Multnomah County — home to Portland — about a half dozen weather shelters were open this week. A similar number of shelters were opened in Seattle’s King County, which also declared an emergency.

Seattle leaders said city shelters will remain open through the new year.

Winter weather and a return to pre-pandemic levels of traffic have resulted in hundreds of accidents on Oregon roads this holiday season.

Oregon Public Broadcasting reported that between Dec. 23 and Dec. 28 there were 915 traffic accidents in the state. During that same period last year there were 365 accidents and 237 in 2019, according to Oregon State Police. The number of deaths has not been calculated yet.

David House, a spokesperson for the Oregon Department of Transportation, said the high number of accidents over the last week is a reminder to travelers to use caution and prepare for slick conditions.

“If you can sit tight for a couple more days, just avoid getting out there, that’s going to be the safest thing you can possibly do,” House said.

In Nevada, a statement released by Gov. Steve Sisolak’s office said the emergency declaration will allow state officials to order vehicles traveling in on mountain highways to turn around and return to lower elevations until weather conditions subside and the roadways are safe to use.

“This will help prevent motorists from becoming stranded overnight on the roadways, potentially running out of gas in subfreezing temperatures without access to emergency services,” the statement said.

It said U.S. 50 and State Routes 207 and 28 were experiencing long delays and dangerous conditions and that authorities need to be able to clear the roadways to make room for emergency vehicles and snow plows.

Caltrans said snowplows were working around the clock and urged people to avoid all but essential travel in the Sierra.

Among staggering snowfall totals in the Sierra, the Northstar resort at Lake Tahoe reported 135 inches (3.43 meters) since Dec. 21.