Seattle to Portland — Weather & Driving Conditions
Driving from Seattle, WA to Portland, OR? This 174-mile route follows I-5. TripCaptain checks the weather at every stop along the way — not just at each end — so you can see where conditions change before you pick a departure time.
What to watch for on this route
TripCaptain flags black ice, dense fog, heavy snow, high wind, heavy rain, and low visibility segment by segment between Seattle, WA and Portland, OR, and gives the trip a clear Hazard Score™ — a 0-100 read where higher is safer.
- Dense Fog: Columbia River valley fog can reduce visibility significantly, especially near the WA-OR border.
- Flooding: Heavy rain events cause standing water and hydroplaning risk on I-5, especially near Centralia and Chehalis.
- Black Ice: Winter mornings in the I-5 corridor between Olympia and Portland see black ice on bridges and overpasses.
When to go, season by season
- Spring (Mar–May): Increasing sunshine. Rain still common but less intense. Pleasant driving conditions.
- Summer (Jun–Aug): Best driving season. Dry and clear with comfortable temps.
- Fall (Sep–Nov): Rain returns in October. Fog events increase. Watch for wet leaves on road surface.
- Winter (Dec–Feb): Frequent rain, occasional snow events. Black ice risk on bridges. I-5 flooding near Chehalis possible.
Pick the safest time to leave
Compare departure windows for Seattle to Portland and choose the one with the lowest risk and the arrival time you want.
Fuel, EV range, and rest stops
See a weather-adjusted fuel or EV energy estimate for the drive, sensible break points across the 174 miles, and a packing list matched to the conditions ahead.