Transportation officials already predicted a peak in traffic congestion over the holiday weekend, but heavy rainfall in northwest Washington may also impact the roads.

The Washington State Department of Transportation shut down an Interstate 5 exit in Bellingham early Sunday because of flooding. It closed Exit 254 northbound, part of the same stretch of highway affected earlier this month by a mudslide event.

Much of northwest Washington is under a flood watch through Monday, including Whatcom, Skagit, Snohomish and King counties, as well as the Olympic Peninsula.

State transportation officials expect higher-than-usual traffic during the Thanksgiving holiday weekend, especially on Interstate 90. And once a roadway reaches capacity, any incidents can cause significant backups, the Washington State Department of Transportation says.

The department released Thanksgiving traffic charts to highlight the best and worst times to travel.

The agency expects congestion or stop-and-go traffic on Interstate 5 from Lacey to Tacoma between 11 a.m. and 6 p.m. Officials expect less congestion southbound on that same stretch, but predict congestion between noon and 3 p.m. nonetheless.

It’s difficult to predict traffic patterns for Interstate 5 northbound near the Canadian border because it only recently reopened, WSDOT said.

Officials also expect congestion or stop-and-go traffic on Interstate 90 eastbound and westbound from Cle Elum to North Bend between 11 a.m. and 4 p.m.