Boulder Climate by Month
Boulder, Colorado, United States
Hot summers and cold winters, with rain spread through the year.
The climate in Boulder is one of hot summers and cold winters, with rain spread through the year. July is the warmest month, with highs around 89°F (32°C); January is the coolest at 47°F (8°C), and nights dip to 19°F (-7°C). About 17 in (421 mm) of rain falls in a typical year, with no clear rainy season. The air is dry, averaging 44% relative humidity.
- Warmest month
- 89°F(32°C)
- Average high, July
- Coldest nights
- 19°F(-7°C)
- Average low, January
- Rain per year
- 17 in(421 mm)
- No clear rainy season
- Humidity
- 44%
- Sunniest: June
Best and worst months in Boulder
Best for weatherMay and September are the best time for weather in Boulder: highs near 75°F (24°C) and about 2.0 in (51 mm) of rain a month.
Least pleasantDecember and January are the least pleasant; January is the coldest, with highs of only 47°F (8°C).
Comfort combines how close the afternoon high is to 75°F (24°C) with how much rain falls and how humid it is. See where the weather is best in September.
Temperature and rain through the year
Highs and lows (°F)
Average highAverage low
Rain (in per month)
Boulder weather by month
| Month | High | Low | Rain | Humidity | Sun |
|---|---|---|---|---|---|
| JanJanuary | 47°F(8°C) | 19°F(-7°C) | 0.6 in(15 mm) | 48% | 2.4 |
| FebFebruary | 47°F(8°C) | 20°F(-7°C) | 0.7 in(18 mm) | 46% | 3.3 |
| MarMarch | 56°F(13°C) | 27°F(-3°C) | 1.5 in(39 mm) | 45% | 4.6 |
| AprApril | 63°F(17°C) | 34°F(1°C) | 2.3 in(58 mm) | 43% | 5.4 |
| MayMayBest | 72°F(22°C) | 43°F(6°C) | 2.6 in(66 mm) | 43% | 6.3 |
| JunJune | 83°F(28°C) | 52°F(11°C) | 1.7 in(42 mm) | 39% | 7.0 |
| JulJuly | 89°F(32°C) | 57°F(14°C) | 1.7 in(43 mm) | 39% | 7.0 |
| AugAugust | 87°F(31°C) | 56°F(13°C) | 1.3 in(34 mm) | 42% | 6.0 |
| SepSeptemberBest | 79°F(26°C) | 47°F(8°C) | 1.4 in(36 mm) | 41% | 5.1 |
| OctOctober | 66°F(19°C) | 36°F(2°C) | 1.2 in(30 mm) | 47% | 3.6 |
| NovNovember | 53°F(12°C) | 26°F(-3°C) | 1.0 in(25 mm) | 49% | 2.6 |
| DecDecember | 47°F(8°C) | 20°F(-7°C) | 0.6 in(15 mm) | 47% | 2.1 |
1991–2020 averages. Sun is solar radiation in kWh/m² per day. Highlighted: the most comfortable months.
Places with a similar climate
All 20 places like Boulder →- 🇺🇸Colorado SpringsColorado, United States · Pop. 457k97%matchSame humiditySimilar rainfallBoulder vs Colorado Springs →
- 🇺🇸Castle RockColorado, United States · Pop. 56k96%matchSame sunshineSimilar rainfallBoulder vs Castle Rock →
- 🇺🇸PuebloColorado, United States · Pop. 109k86%matchSame winter lowsSame humidityBoulder vs Pueblo →
- 🇺🇸CheyenneWyoming, United States · Pop. 65k82%matchSame winter lowsSimilar rainfallBoulder vs Cheyenne →
- 🇵🇰ThalKhyber Pakhtunkhwa, Pakistan · Pop. 29k74%matchSame humidityWetter wintersBoulder vs Thal →