Cornelius, Oregon Weather Climate

Learn about Cornelius, Oregon Weather and Climate

Curious about Cornelius, Oregon Weather & Climate? Here’s the simple version: Cornelius has mild, wet winters and warm, dry summers. This guide explains what the seasons feel like, what to pack, and how local weather affects daily life—from winery visits to driving over the Coast Range.

Quick Answer

Cornelius has a classic western Oregon pattern: rainy, cool winters and dry, pleasant summers. Expect winter highs near 45–50°F with frequent rain and occasional frost or light snow; summer highs around 75–85°F with cool nights. Most rain falls November–March. Heatwaves and wildfire smoke can happen in late summer but aren’t daily occurrences.

What Cornelius, Oregon Weather & Climate Means

When people say “Cornelius, Oregon Weather & Climate,” they mean a mild, maritime-influenced climate in the Tualatin Valley. You’ll see:

  • Wet season (late fall through early spring): grey skies, steady light-to-moderate rain, and morning fog.
  • Dry season (late spring through early fall): long, sunny days and comfortable temperatures.
  • Annual precipitation: roughly 40–45 inches, heavier near the Coast Range west of Forest Grove.
  • Köppen style: warm-summer Mediterranean (dry summers, wet winters), in everyday terms: “cool and damp, then warm and dry.”

Why People Search for This in Cornelius, Oregon

  • Daily life: Planning school runs, commuting on Tualatin Valley Hwy (Hwy 8), or weekend trips.
  • Outdoor fun: Wineries, U-pick farms, and nearby birding at Fernhill Wetlands or Jackson Bottom.
  • Day trips: Hagg Lake (about 12 miles south) and the Oregon Coast via Hwy 6 (check winter road conditions).
  • Moving here: Understanding heating needs, garden choices, and how often it rains.

What to Expect

Season by season:

  • Winter (Dec–Feb)

    • Highs: 45–50°F; Lows: 33–38°F
    • Frequent rain, fog, and a few icy mornings. Light snow is possible some years.
    • Occasional Pacific windstorms can bring 30–45 mph gusts.
    • Roads are usually clear in town, but black ice can form overnight. Hwy 6 to the Coast may require chains.

  • Spring (Mar–May)

    • Highs: 55–70°F, variable days
    • Showers and sunbreaks; gardens turn lush. Tree and grass pollen rise.
    • Trails at Fernhill Wetlands and forested parks can be muddy—wear waterproof shoes.

  • Summer (Jun–Sep)

    • Highs: 75–85°F most days; nights often 50–58°F
    • Dry, sunny, and comfortable; July–August are driest.
    • Heatwaves can push 90–100°F+ a few days each summer.
    • Sometimes wildfire smoke drifts in late summer; check air quality before big hikes.

  • Fall (Oct–Nov)

    • Highs: 55–65°F
    • Crisp mornings, colorful vineyards, and a steady return of rain by November.
    • Early fog is common in the valley.

Local notes:

  • Microclimates: Areas closer to the Coast Range (Forest Grove, Hagg Lake) run slightly cooler and wetter than central Cornelius. Afternoon breezes usually come from the west.
  • Daylight: Late June sunsets after 9 pm; in December, sunset is around 4:30 pm.

Tips for Visitors / Residents

  • Always pack layers. A waterproof jacket with a hood beats an umbrella on breezy days.
  • Footwear matters. Waterproof shoes for parks and farms; sandals or breathable shoes in summer.
  • Driving tips:
    • In winter, watch for slick spots at dawn.
    • If heading to the Coast on Hwy 6, check chain requirements and road cameras.
  • Beat the heat: Plan outdoor activities before 11 am on hot days; evenings cool off nicely.
  • Allergies: Tree pollen peaks in spring; grass in late spring/early summer. Mold can be higher in wet months.
  • Best time to visit for outdoor plans: July–September for the steadiest sun. May–June are green and pleasant with occasional showers.

Best Local Resources

  • National Weather Service (Portland): Detailed forecasts, wind advisories, and radar.
  • ODOT TripCheck: Live road cameras and alerts for Hwy 8, Hwy 47, and Hwy 6.
  • AirNow / Oregon DEQ: Current air quality and wildfire smoke maps.
  • Washington County Roads: Local closures and storm response.
  • Portland General Electric Outage Map: Power outage and restoration updates.
  • City of Cornelius & Washington County Alerts: Local emergency notifications.

Search any of the above by name to get the latest links and maps.

Frequently Asked Questions About Cornelius, Oregon Weather & Climate

  • How far is Cornelius from Portland?

    • About 25 miles west of downtown Portland; roughly 45–60 minutes by car depending on traffic.

  • What’s the best time of year to visit?

    • For reliably dry weather, July–September. For greenery and fewer crowds, May–June and late September–October.

  • Does it snow in Cornelius?

    • Occasionally. Some winters see a light snowfall or two; many winters have none at valley level. Icy mornings are more common than heavy snow.

  • Is summer very hot?

    • Most summer days are 75–85°F with cool evenings. Expect a few 90–100°F days during heatwaves.

  • Will I need chains to drive around town in winter?

    • In town, usually no. But if you’re driving Hwy 6 over the Coast Range or into higher elevations, carry chains and check conditions.

Summary

Cornelius enjoys mild, rainy winters and warm, dry summers. Rain is concentrated from November to March; summers are sunny with cool nights. Plan for layers, waterproof shoes in the wet season, sun protection in summer, and check road conditions if heading toward the Coast Range.

  • Best Time to Visit Cornelius, Oregon
  • Outdoor Things to Do Near Cornelius (Wineries, Hagg Lake, Wetlands)
  • Moving to Cornelius: Neighborhoods, Commute, and Daily Life
  • Getting Around the Tualatin Valley (Hwy 8, Hwy 47, and Transit)