Jefferson County Climate
Jefferson County, Colorado
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
47.7°F
Annual Precip
19.8"
Annual Snowfall
95.9"
Extreme Heat Days
21
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
6a
Minimum winter temperature range for plant survival
2,221
Favors cool-season crops
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Jefferson County
Climate Verdict
Jefferson County has a cool, averaging 47.7°F annually, semi-arid conditions with only 19.8 inches of annual precipitation, occasional hot days — 21.47142857142857 per year above 90°F, heavy winter snowfall averaging 95.9 inches per year. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are cold, with January averaging 30.5°F. summers are pleasantly cool with July averaging 69.4°F. The 39°F seasonal variation provides noticeable but manageable change. December is typically the coldest month and July the warmest.
Outdoor & Gardening Guidance
Winter sports enthusiasts benefit from reliable snow cover for 3-4 months annually.
Regional Context
Jefferson County closely matches the Colorado statewide average temperature of 45.9°F, it is somewhat wetter than average for Colorado.
Climate Profile
About Jefferson County Weather
Jefferson runs 14° cooler than U.S. median
Jefferson County's 47.7°F annual temperature sits 14 degrees below the U.S. median of 61.7°F, reflecting its high-elevation location near Denver's western foothills. Its 19.8 inches of annual precipitation exceed both the state average (16.0 inches) and national average (15.2 inches), making it Colorado's wetter mountain region.
Slightly above Colorado's average
At 47.7°F, Jefferson County runs 1.7 degrees above Colorado's state average of 46.0°F, ranking it in the warmer half of the state's 64 counties. Its 21 extreme heat days annually place it solidly above mountain peers but well below the eastern plains.
Mountain buffer between highlands and plains
Jefferson (47.7°F) sits warmer than the extreme-cold Gunnison and Jackson counties but cooler than the plains-influenced Kiowa and Kit Carson counties to the east. At 21 extreme heat days, Jefferson experiences notably more hot weather than alpine neighbors but far less than eastern counties.
Moderate winters, warm summers, occasional extremes
January averages 30.5°F and July reaches 69.4°F, creating a 39-degree swing with 21 days above 90°F annually. Jefferson receives 95.9 inches of snow yearly, requiring serious winter infrastructure but far less than high-mountain counties.
Balance mountain snow with summer cooling needs
Jefferson residents need reliable heating for winter snowpack (95.9 inches annually) and standard air-conditioning for 21 hot summer days. Spring and fall transition planning is critical for outdoor recreation, with May-September offering prime windows for hiking, water activities, and construction work.
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.