Contra Costa County Climate
Contra Costa County, California
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
60.4°F
Annual Precip
19.4"
Annual Snowfall
0.1"
Extreme Heat Days
40
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
9b
Minimum winter temperature range for plant survival
4,076
Excellent for heat-loving crops
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Contra Costa County
Climate Verdict
Contra Costa County has a warm, averaging 60.4°F year-round, semi-arid conditions with only 19.4 inches of annual precipitation, occasional hot days — 40.11666666666667 per year above 90°F, light snow averaging 0.1 inches per year. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are mild, with January temperatures averaging 48.6°F. summers are warm — July averages 71.3°F. The climate is remarkably stable year-round, with only a 23°F difference between January and July. December is typically the coldest month and July the warmest.
Outdoor & Gardening Guidance
The moderate temperatures support hiking, cycling, and camping comfortably in spring, summer, and fall.
Regional Context
Contra Costa County closely matches the California statewide average temperature of 58.7°F, it is also noticeably drier, receiving 6.4 inches less precipitation than the state average, the county experiences 18.554258296267207 fewer extreme heat days than the state average.
Climate Profile
About Contra Costa County Weather
A Warm and Steady Bay Climate
Contra Costa County averages 60.4°F, putting it comfortably above the median temperature for the United States. Its weather is characterized by mild winters and warm, dry summers.
Warmer and Drier Than State Averages
The county is warmer than the California average of 58.7°F. Its 19.4 inches of annual precipitation is about 6 inches lower than the state's 25.8-inch average.
Warmer and Drier than Alameda
Contra Costa is slightly warmer and drier than its neighbor Alameda County. While Alameda receives 18.1 inches of rain, Contra Costa receives 19.4 but has 14 more extreme heat days.
Forty Days of Heat and Zero Snow
July averages 71.3°F, contributing to 40 extreme heat days each year. Winter is very mild at 49.6°F with virtually no snow recorded annually.
Invest in Cooling for 40 Heatwaves
Air conditioning is essential for the 40 days of temperatures over 90°F. Because snow is non-existent, residents should prioritize summer gear and water-efficient landscaping.
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.