If you’re planning to travel to Oregon or Idaho to watch the August 21 eclipse, plan ahead and don’t be surprised if you run into major traffic.

The Oregon Department of Transportation expects the eclipse to be the biggest traffic event in the state’s history drawing about 1 million people to the zone of totality to view the event.

The path of totality stretches from Salem at 10:18 a.m. to Madras at 10:21 p.m. to Baker City at 10:25 a.m.

Avoid sitting in traffic

Officials are advising people to arrive early, stay put, and stay late to avoid the worst of the traffic crunch. If you can, drive down to Oregon on Saturday and stay past Monday.

“It's not a one-day deal," said Bart Treece, Washington State Department of Transportation southwest region communications manager.

Vancouver, Wash. hotels are sold out on Sunday night, but they’re also 80 percent booked on Monday night, suggesting many people will stay past the eclipse, according to Treece.

Resources: Oregon road maps | Oregon TripCheck travel info | Traffic alerts

WSDOT expects major thoroughfares into Oregon will be slow going, including the following highways:

Interstate 5 – Vancouver to Eugene
Interstate 82 – Benton County
US 97 – Klickitat County
State Route 14 – Columbia River Gorge
US 197 – Dallesport
Interstate 205 – Clark County to Portland
State Route 433 – The Lewis and Clark Bridge in Longview
State Route 4 – Longview to Naselle
State Route 401 – Naselle to Dismal Nitch
US 101 – Ilwaco to Astoria

Oregon does not anticipate closing any state highways, but they may restrict left turns to keep traffic moving.

Eclipse road trip tips

Don’t wear eclipse glasses while driving. If the glasses do what they’re supposed to, you won’t be able to see anything but the sun.

Don’t camp out at rest stops. Rest areas are designated for travelers who are not staying longer than eight hours.

Don’t park your car on the shoulder. If you want to pull off the highway to watch the eclipse, don’t use the shoulder. It may be needed for emergency vehicles to get through. Your car could also start a brush fire.

Drew Mikkelsen contributed to this report.