Washington County Climate
Washington County, Oregon
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
53.5°F
Annual Precip
41.5"
Annual Snowfall
4.0"
Extreme Heat Days
18
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
8b
Minimum winter temperature range for plant survival
2,418
Favors cool-season crops
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Washington County
Climate Verdict
Washington County has a mild, with an average annual temperature of 53.5°F, moderately wet with 41.5 inches of annual precipitation, rare extreme heat with only 17.625 days above 90°F annually, light snow averaging 4.0 inches per year. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are mild, with January temperatures averaging 41.5°F. summers are pleasantly cool with July averaging 67.9°F. The climate is remarkably stable year-round, with only a 26°F difference between January and July. December is typically the coldest month and August the warmest.
Outdoor & Gardening Guidance
Growing season and gardening data is currently limited for Washington County. Check the USDA Plant Hardiness Zone Map and local extension office for specific guidance.
Regional Context
Washington County is 3.1°F warmer than the Oregon statewide average of 50.5°F, it is somewhat wetter than average for Oregon.
Climate Profile
About Washington County Weather
Matching the National Average Perfectly
Washington County's average temperature of 53.5°F aligns exactly with the national median. This marine-influenced climate offers stable temperatures without the extreme fluctuations found in the Midwest.
One of Oregon’s Warmest, Wettest Hubs
The county stays 3 degrees warmer than the state average of 50.5°F. It also receives 41.5 inches of annual precipitation, outpacing the Oregon state average of 37.4 inches.
Consistent With the Willamette Valley Profile
Its climate closely mirrors Multnomah County, though it often stays slightly drier than the deepest parts of the valley. It remains warmer and more developed than the rugged coastal counties to the west.
Mild Summers and Wet, Green Winters
Summers are temperate with only 18 days above 90°F and a comfortable 66.0°F average. Winters are dominated by rain rather than ice, seeing only 4.0 inches of snow and a January average of 41.5°F.
Rain Gear is the Primary Priority
With 41.5 inches of annual rain, high-quality waterproof gear is essential for daily life. Since extreme heat is limited to just 18 days, many residents prioritize moisture control and drainage over heavy-duty air conditioning.
Frequently Asked Questions
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Data sources: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020. Forecast and alert data from National Weather Service API. Air quality data from Open-Meteo.
Climate normals are 30-year averages of weather variables. Station data is aggregated to county level. Forecasts and alerts are fetched live and may change frequently. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.