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

In the planner, TripCaptain highlights forecast weather risks between Seattle, WA and Portland, OR and summarizes the analysis with a Hazard Score™ from 0 to 100. A higher score indicates lower forecast risk, without guaranteeing road conditions.

• 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.

Compare departure times

Open Seattle to Portland in the planner to check the forecast for your date and compare nearby hours within your plan's limits. Save the trip to follow changing conditions in Live Mode.

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.

Browse all popular routes