Boulder (CO) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Boulder.
Climate overview of Boulder
Boulder, in Colorado, United States, experiences noticeable changes in temperature across the year. Summers can be very warm, while winters often bring cold and occasional snow. Precipitation remains moderate and is spread fairly evenly over the months. The city attracts visitors not only for its mountain trails and active lifestyle but also for its strong focus on wellness and spiritual practices. Boulder has a long-standing community centered around yoga, meditation, and holistic health. Now, let’s explore all the climate details to give you a complete picture.
Boulder Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Boulder — and find the best time to visit.
Monthly Temperature in Boulder
The climate in Boulder is known for significant temperature differences throughout the year, making the weather dynamic. On average, daytime temperatures range from a very warm 31°C (88°F) in July to a chilly 7°C (45°F) in December.
Nighttime temperatures range from 15°C (59°F) in July to -7°C (19°F) in December.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Boulder
Generally, Boulder receives mid-range precipitation levels, with 513 mm (20 in) annually. The seasons in Boulder bring significant changes in precipitation. The wettest month, May, receives moderate rainfall, with an average of 80 mm (3.1 in) of precipitation. This rainfall is distributed across 12 rainy days.
In contrast, the driest month, January, experiences much less snowfall, totaling 16 mm (0.6 in) over 5 snowy days. These distinct seasonal differences provide diverse experiences throughout the year. For more details, please visit our Boulder Precipitation page.
The mean monthly precipitation over the year, including rain, hail, and snow
The average number of days each month with precipitation
Sunshine Hours in Boulder
In Boulder, summer days are longer and more sunny, with daily sunshine hours peaking at 10.8 hours in July. As the darker season arrives, the brightness of the sun becomes less. November sees a soft sun for only 6.5 hours per average day.
Visit our detailed sunshine hours page for more information.
Monthly hours of sunshine
Daily hours of sunshine
Daily percentage of sunshine
Humidity in Boulder by Month
The relative humidity is moderate throughout the year in Boulder.
The city experiences its highest humidity in December, reaching 56%. In July, the humidity drops to its lowest level at 46%. What does this mean? Read our detailed page on humidity levels for further details.
Relative humidity over the year
Best Time to Visit Boulder
Frequently asked questions about the climate in Boulder
What is the best time to visit Boulder?
May, June and September typically offer the most optimal weather in Boulder. In contrast, December tends to have less optimal conditions. Boulder has a distinct dry season from November to February.
What temperatures can I expect in Boulder?
Daytime highs range from 7°C (45°F) in December to 31°C (88°F) in July. Nighttime lows range from -7°C (19°F) to 15°C (59°F). Temperatures vary considerably through the year.
How much rain does Boulder get?
Annual rainfall is around 513 mm (20 in). May is the wettest month with 80 mm (3.1 in), while January is the driest with 16 mm (0.6 in).
How sunny is Boulder?
Boulder receives around 3,102 hours of sunshine per year. July is the sunniest month with 323 hours, while November is the cloudiest with just 195 hours. Overall, Boulder enjoys abundant sunshine.
Boulder 3-Day Forecast
Boulder (CO) 3-Day Forecast
Boulder on the map
Boulder is highlighted — select any city to see its climate.
Popular this month
Where to go in July — average daytime high across popular destinations.
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