Boulder, United States experiences average highs of 17°C (63°F) and lows of 2°C (36°F) throughout the year. Rainfall is moderate, averaging about 10 rainy days per month. Sunshine is abundant, averaging about 10 hours per day. Average highs have stayed broadly stable across the available records.
Boulder, United States Weather & Climate 2026
Monthly climate averages for Boulder, United States. Based on 10-year ERA5 reanalysis data.
Climate Overview
Drier season: Jan–Dec 
Wetter season: Mar–Aug At-a-Glance Climate Summary
Live Weather & Air Quality
Key figures
Climate Score
5.1/10
Best: June, July, August, September
UV Index
6
High
Temperature 17°C / 2°C
Feels Like 15°C / -1°C
Rainy Days 10
Rainfall 54 mm
Sunshine 10 h
Humidity 60%
Wind Speed 14 km/h
Dew Point 2°C
Snow Days 8 days
Frost Days 19 days
Hottest Month
30°C
July
Avg Low15°C
Rain16days
Coldest Month
-10°C
January
Avg High4°C
Rain6days
Driest Month
5days
November
Avg High12°C
Avg Low-3°C
Windiest Month
15 km/h
April (Gusts 37)
Worst Time to Visit
Consider avoiding January, February, March, December due to very cold temperatures.
Sun Position
Sunrise 05:33
Daylight 15h
Sunset 20:33
Live conditions—
Boulder on the map · live conditions
Boulder, United States
- Continent
- Americas
- Country
- United States
- City
- Boulder
- Population
- 106.8K
- Elevation
- 1,624 m
- Coordinates
- 40.01°, -105.27°
Seasonal Breakdown
Spring
Mar–May
Avg High 16°C
Avg Low 0°C
Rain 13 days/mo
Summer
Jun–Aug
Avg High 29°C
Avg Low 13°C
Rain 14 days/mo
3/3 best months
Autumn
Sep–Nov
Avg High 19°C
Avg Low 4°C
Rain 7 days/mo
1/3 best months
Winter
Dec–Feb
Avg High 6°C
Avg Low -8°C
Rain 6 days/mo
Climate Charts
Based on historical averages (2016–2025)
Monthly Temperatures
HighLowShaded bands show the typical range across the available yearly records.
Line chart showing monthly temperatures. Jan: 4°C / -10°C . Feb: 6°C / -9°C . Mar: 11°C / -4°C . Apr: 16°C / 0°C . May: 20°C / 5°C . Jun: 27°C / 12°C . Jul: 30°C / 15°C . Aug: 29°C / 14°C . Sep: 27°C / 10°C . Oct: 19°C / 3°C . Nov: 12°C / -3°C . Dec: 7°C / -7°C .
Monthly Rainfall
Rainfall
Bar chart showing monthly rainfall. Jan: 28 mm. Feb: 34 mm. Mar: 59 mm. Apr: 61 mm. May: 122 mm. Jun: 78 mm. Jul: 70 mm. Aug: 68 mm. Sep: 43 mm. Oct: 36 mm. Nov: 28 mm. Dec: 23 mm.
Monthly Humidity
Humidity
Line chart showing monthly humidity. Jan: 68%. Feb: 64%. Mar: 63%. Apr: 60%. May: 65%. Jun: 57%. Jul: 55%. Aug: 55%. Sep: 53%. Oct: 55%. Nov: 60%. Dec: 61%.
Monthly Wind Speed
Wind SpeedGusts
Bar chart showing monthly wind speed. Jan: 14 km/h . Feb: 15 km/h . Mar: 15 km/h . Apr: 15 km/h . May: 14 km/h . Jun: 14 km/h . Jul: 14 km/h . Aug: 13 km/h . Sep: 13 km/h . Oct: 14 km/h . Nov: 14 km/h . Dec: 15 km/h .
Sunshine
Sunshine
Sunshine: Jan: 8h. Feb: 9h. Mar: 10h. Apr: 11h. May: 12h. Jun: 13h. Jul: 13h. Aug: 12h. Sep: 11h. Oct: 10h. Nov: 8h. Dec: 8h.
UV Index
UV Index
Bar chart showing monthly UV index. Jan: UV 3. Feb: UV 4. Mar: UV 6. Apr: UV 7. May: UV 8. Jun: UV 8. Jul: UV 8. Aug: UV 8. Sep: UV 7. Oct: UV 5. Nov: UV 4. Dec: UV 3.
Monthly Daylight Hours
Daylight12h reference
Monthly Dew Point & Comfort
Dew Point Dry Comfortable Humid Muggy Oppressive
Snow Days
Snow DaysSnowfall
Snow Days: Jan: 10 days. Feb: 12 days. Mar: 14 days. Apr: 11 days. May: 7 days. Jun: 0 days. Jul: 0 days. Aug: 0 days. Sep: 1 days. Oct: 5 days. Nov: 7 days. Dec: 9 days.
Climate Trends
Average highs have stayed broadly stable across the available records. Average rainfall is trending wetter by about 14 mm.
2016 to 2025
Avg high Avg rainfall
Climate summary
| Last 12 months | All years | |
|---|---|---|
| Hottest month | Jul 2025 · 30°C | Jul · 30°C |
| Coldest month | Jan 2025 · -13°C | Jan · -10°C |
| Wettest month | May 2025 · 142 mm | May · 122 mm |
| Windiest month | Mar 2025 · 16 km/h | Apr · 15 km/h |
Month-by-Month Weather Table
January
Poor 
February
Poor March
Poor April
Poor May
Fair June best
Excellent July best
Excellent August best
Excellent September best
Excellent October
Fair November
Poor December
Poor | Month | Temp | Feels Like | Rain | Sun | Humidity | UV | Status | Details |
|---|---|---|---|---|---|---|---|---|
| January | 4°C / -10°C | 1°C / -15°C | 6days (28 mm) Good | 7.9h Good | 68% Muggy | 3.2 Moderate | Poor | View Details |
| February | 6°C / -9°C | 3°C / -14°C | 8days (34 mm) Wet | 9.1h Good | 64% Muggy | 4.4 Moderate | Poor | View Details |
| March | 11°C / -4°C | 8°C / -9°C | 10days (59 mm) Wet | 10.2h Excellent | 63% Muggy | 5.8 High | Poor | View Details |
| April | 16°C / 0°C | 13°C / -4°C | 11days (61 mm) Wet | 11.2h Excellent | 60% Moderate | 6.9 High | Poor | View Details |
| May | 20°C / 5°C | 18°C / 2°C | 17days (122 mm) Wet | 12h Excellent | 65% Muggy | 7.7 Very High | Fair | View Details |
| June best | 27°C / 12°C | 27°C / 10°C | 14days (78 mm) Wet | 13.3h Excellent | 57% Moderate | 8.1 Very High | Excellent | View Details |
| July best | 30°C / 15°C | 30°C / 14°C | 16days (70 mm) Wet | 13.1h Excellent | 55% Moderate | 8.3 Very High | Excellent | View Details |
| August best | 29°C / 14°C | 29°C / 13°C | 13days (68 mm) Wet | 12.1h Excellent | 55% Moderate | 7.6 Very High | Excellent | View Details |
| September best | 27°C / 10°C | 25°C / 8°C | 9days (43 mm) Wet | 11.1h Excellent | 53% Moderate | 6.5 High | Excellent | View Details |
| October | 19°C / 3°C | 16°C / 0°C | 7days (36 mm) Good | 9.6h Good | 55% Moderate | 5.1 High | Fair | View Details |
| November | 12°C / -3°C | 8°C / -7°C | 5days (28 mm) Good | 8.3h Good | 60% Moderate | 3.5 Moderate | Poor | View Details |
| December | 7°C / -7°C | 3°C / -11°C | 5days (23 mm) Good | 7.6h Good | 61% Muggy | 2.8 Moderate | Poor | View Details |
Compare Nearby City Climates
Frequently Asked Questions
The best months to visit Boulder are June, July, August, September, when temperatures are comfortable and rainfall is at its lowest. This is based on 10-year climate averages for Boulder, scoring temperature, rainfall, humidity, and sunshine hours.
The hottest month in Boulder is July, with average daytime highs of 30°C (86°F). Plan outdoor activities for early morning or late afternoon if visiting during this period.
The coldest month in Boulder is January, with average overnight lows of -10°C (15°F). Pack warm layers and expect shorter daylight hours during this period.
The wettest month in Boulder is May, averaging 122mm of precipitation across 17 rainy days. An umbrella or waterproof jacket is essential.
The rainy season in Boulder runs through May, July, June, August, with the heaviest rainfall in May. Based on 10-year averages for Boulder.
Boulder receives approximately 125 sunshine hours per year. The sunniest month is June with around 13 hours. Based on climate data for Boulder.
The least favorable months to visit Boulder are January, February, March, December, primarily due to very cold temperatures. For the best conditions, consider June, July, August, September instead.
The annual average UV index in Boulder is 6, classified as high. Standard sun protection (sunscreen, hat) is recommended during prolonged outdoor exposure.
Average humidity in Boulder is 60%, classified as moderate. Humidity levels are generally comfortable and should not affect outdoor activities for most people.
Yes, Boulder receives snow. Months with snowfall average 8 snow days and 17 cm (7 in) of accumulation, with about 19 frost days during winter.
Average wind speeds in Boulder are 14 km/h (9 mph). The windiest month is April with peak winds reaching 15 km/h (10 mph) (gusts up to 37 km/h / 23 mph).
Boulder averages 7 clear-sky days per month with overall cloud cover around 44%. The clearest skies occur in October.
The annual average dew point in Boulder is 2°C (36°F), which feels dry and comfortable. Outdoor activities are comfortable year-round from a humidity standpoint.
Boulder has a Humid Subtropical climate, classified as Cfa under the Köppen system. Temperate climates have mild winters and warm summers, with rainfall spread across the year and four distinct seasons.
The 'feels like' temperature in Boulder ranges from -1°C (30°F) to 15°C (59°F) on average. Wind chill makes winters feel noticeably colder than the actual temperature — layered clothing is recommended.
Yes, June is a great time to visit Boulder. It earns a climate score of 8.3/10 with Excellent.
For June in Boulder, pack Warm evening layer, Umbrella, Waterproof jacket, Waterproof shoes, Breathable clothing. With average highs of 27°C (81°F) and 14 rainy days, these essentials will keep you comfortable.
Data Source
Climate data derived from ERA5 reanalysis (ECMWF), averaged over 2016–2025. Sea surface temperature from marine reanalysis data. Climate scores and seasonal estimates are computed by WorldStats.
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