San Mateo County Climate
San Mateo County, California
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
57.6°F
Annual Precip
25.4"
Annual Snowfall
0.0"
Extreme Heat Days
14
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
10a
Minimum winter temperature range for plant survival
2,921
Supports most vegetables & fruits
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: San Mateo County
Climate Verdict
San Mateo County has a mild, with an average annual temperature of 57.6°F, moderate rainfall of 25.4 inches per year, rare extreme heat with only 13.600000000000001 days above 90°F annually, virtually no measurable snowfall. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are mild, with January temperatures averaging 50.6°F. summers are pleasantly cool with July averaging 63.9°F. The climate is remarkably stable year-round, with only a 13°F difference between January and July. December is typically the coldest month and August the warmest.
Outdoor & Gardening Guidance
The moderate temperatures support hiking, cycling, and camping comfortably in spring, summer, and fall.
Regional Context
San Mateo County closely matches the California statewide average temperature of 58.7°F, the county experiences 45.07092496293387 fewer extreme heat days than the state average.
Climate Profile
About San Mateo County Weather
A Mild Mediterranean Climate Near the Coast
San Mateo's average annual temperature of 57.6°F is warmer than the national median. This reflects a stable, temperate climate that avoids the extreme fluctuations seen in the interior U.S.
Cooler Than the California Average
The county's 57.6°F average is slightly cooler than the California state average of 58.7°F. It ranks in the middle-to-lower tier of warmth among the state's 58 counties.
Moderate Rain Compared to Bay Area Neighbors
With 25.4 inches of annual precipitation, San Mateo is drier than Santa Cruz to the south. However, it receives more moisture than the 21.2 inches recorded in Santa Clara.
Temperate Summers and Frost-Free Winters
July temperatures average a mild 63.9°F, and the county sees only 14 days of extreme heat per year. Snow is non-existent, while winter averages remain comfortable at 51.1°F.
Layered Clothing and Minimal HVAC Needs
The marine influence means residents rarely need heavy heating or cooling systems. Focus on layered clothing to manage the transition from foggy mornings to sunny afternoons.
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.