If the holidays involve hitting the road, idling in ferry lanes or lingering in airports, then plan to leave early and be prepared for the worst.

Weather can havoc even the best laid plans.

Traffic annually cranks up heading into Christmas and around New Year’s Day. It means congested highways, long vehicle queues for cars and busy airport terminals, even without the cold and snow.

Sea-Tac topped FlightAware’s “Misery Map” on Tuesday morning, with 191 cancellations and 49 delays.

Washington State Ferries advised passengers to check mobile app and online alerts before traveling due to potential sailing delays.

It's snowy at many of our terminals, especially the farther north you go. If you must travel with us today, please use extra caution while navigating through our facilities, clear your vehicle of snow & ice and check terminal conditions in advance: https://t.co/abcjy5VnR9 #wawx pic.twitter.com/jq78HNkmsA

— Washington State Ferries (@wsferries) December 20, 2022

INRIX, a transportation data company based in Kirkland, estimates over 112 million people across the country are traveling more than 50 miles from home this season. That would make it the third-busiest travel holiday season since 2000, when AAA started tracking the data.

The vast majority of those travelers, around 102 million, will be driving, according to INRIX projections.

On the roads, the major delays are likely on I-5 as well as across mountain passes on I-90 and U.S. 2, according to the Washington State Department of Transportation. The WSDOT app and website, wsdot.com/travel, has real-time updates.

On Tuesday, at Stevens Pass on U.S. 2 and Snoqualmie Pass on I-90, chains were required on all vehicles except those with all-wheel drive. Oversize vehicles were prohibited on Stevens Pass.

All winter drivers, and especially those headed across the mountains, should be prepared for bad weather, state transportation staff said. That means having an emergency kit with food, water and warm clothes, as well as chains or studded tires in case they’re required on the passes.

“It takes just one reckless person driving too fast, under the influence or not following chain requirements to close a mountain pass for all of us,” WSDOT winter program manager Jim Andersen wrote in a press release. “Our crews take great pride in their work and do everything in their power to keep roads open — but we need drivers and truckers to do their part and slow down.”

U.S. 2 between Skykomish and Stevens Pass is expected to see higher-than-average eastbound traffic starting Dec. 22 (Thursday morning). Eastbound traffic could spike Friday morning and afternoon and continue to be above normal through Christmas Day and Monday, Dec. 26.

Westbound traffic on the highway is projected to rise similarly, with a spike Friday afternoon and another from morning to evening Monday.

The worst congestion in the Seattle area is expected to be through Tacoma between 6 and 8 p.m. Dec. 28 on I-5 south, according to INRIX.

The day after Christmas is a busy time for shoppers returning unwanted gifts and scooping up deals on holiday items for next year.

Ferry travelers can skirt what are expected to be long waits by walking on instead of driving. The Washington State Ferries system is expecting busy travel the Friday and Saturday before Christmas and New Year’s Day in both directions.