Napa County Climate
Napa County, California
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
59.5°F
Annual Precip
31.2"
Annual Snowfall
0.0"
Extreme Heat Days
49
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
9b
Minimum winter temperature range for plant survival
3,820
Supports most vegetables & fruits
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Napa County
Climate Verdict
Napa County has a mild, with an average annual temperature of 59.5°F, moderate rainfall of 31.2 inches per year, occasional hot days — 48.5 per year above 90°F, 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 48.2°F. summers are warm — July averages 71.0°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
Napa County closely matches the California statewide average temperature of 58.7°F, it is also noticeably wetter, receiving 5.4 inches more precipitation than the state average.
Climate Profile
About Napa County Weather
Warm and Mediterranean
Napa County enjoys a warm 59.5°F annual average, placing it well above the national median temperature. This climate provides the ideal heat accumulation for world-class viticulture.
Warmer and Wetter Than Average
Napa is slightly warmer than the 58.7°F state average and notably wetter, receiving 31.2 inches of rain annually. This exceeds the California average of 25.8 inches, fueling its lush valley floor.
Hotter Summers Than Monterey
Compared to coastal Monterey, Napa is significantly warmer in the summer with a July average of 71.0°F. It also receives about 11 inches more rain per year than its southern coastal counterparts.
A Season of Sun and Rain
The county experiences 49 extreme heat days annually, marking a punishing summer season. Winters are wet but mild, with no recorded snowfall and a January average of 48.2°F.
Manage the Summer Heatwaves
Robust HVAC systems are a must to handle the 49 days of temperatures over 90°F. Homeowners should also maintain clear gutters to handle the 31.2 inches of concentrated winter rainfall.
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.