City in Colorado, United States
Boulder weather by month and the best time to visit
When to go to Boulder
May–Jun and Sep–Oct are mild and sunny. Jul–Aug is hot with afternoon storms; Dec–Mar is cold with occasional heavy snow that clears quickly.
Boulder weather by month
Average daily high, rainfall and conditions.
- Jan6°20 mm
- Feb7°24 mm
- Mar13°36 mm
- Apr17°54 mm
- May23°65 mm
- Jun30°43 mm
- Jul33°52 mm
- Aug31°43 mm
- Sep27°36 mm
- Oct19°33 mm
- Nov12°21 mm
- Dec6°21 mm
Monthly averages
| Month | High | Low | Rain | Humidity | Conditions |
|---|---|---|---|---|---|
| January | 6°C43°F | -5°C23°F | 20 mm | 55% | Cold |
| February | 7°C44°F | -5°C22°F | 24 mm | 56% | Cold |
| March | 13°C55°F | -2°C29°F | 36 mm | 51% | Cool |
| April | 17°C63°F | 2°C35°F | 54 mm | 49% | Cool |
| May | 23°C73°F | 7°C44°F | 65 mm | 49% | Pleasant |
| June | 30°C87°F | 13°C56°F | 43 mm | 41% | Pleasant |
| July | 33°C91°F | 17°C63°F | 52 mm | 42% | Hot |
| August | 31°C88°F | 16°C61°F | 43 mm | 43% | Pleasant |
| September | 27°C80°F | 11°C52°F | 36 mm | 42% | Pleasant |
| October | 19°C65°F | 4°C38°F | 33 mm | 47% | Pleasant |
| November | 12°C53°F | -2°C29°F | 21 mm | 51% | Cool |
| December | 6°C42°F | -6°C22°F | 21 mm | 57% | Cold |
Best months across United States
| Place | Best months | Warmest month |
|---|---|---|
| New York City | Apr–Jun, Sep–Oct | Jul (26°C) |
| Las Vegas | Mar–May, Oct–Nov | Jul (42°C) |
| Los Angeles | Mar–May, Sep–Nov | Aug (32°C) |
| Orlando | Feb–Apr, Nov | May (31°C) |
| Miami | Nov–Apr | Aug (30°C) |
| San Francisco | Apr–May, Sep–Oct | Sep (24°C) |
| Honolulu | Apr–Jun, Sep–Oct | Sep (28°C) |
| Washington, D.C. | Mar–May, Sep–Oct | Jul (31°C) |
| Chicago | May–Jun, Sep–Oct | Jul (25°C) |
| Boston | May–Jun, Sep–Oct | Jul (28°C) |
| New Orleans | Feb–Apr, Oct–Nov | Jul (30°C) |
| San Diego | Apr–May, Sep–Nov | Aug (32°C) |
| Seattle | Jun–Sep | Aug (24°C) |
| Maui | Apr–May, Sep–Oct | Sep (22°C) |
| Nashville | Apr–May, Sep–Oct | Aug (32°C) |
| Austin | Mar–May, Oct–Nov | Aug (36°C) |
| Miami Beach | Nov–Apr | Aug (30°C) |
| Key West | Dec–Apr | Aug (30°C) |
| Denver | May–Jun, Sep–Oct | Jul (33°C) |
| Philadelphia | Apr–May, Sep–Oct | Jul (30°C) |
| Portland | Jun–Sep | Aug (29°C) |
| Atlanta | Mar–May, Oct–Nov | Jul (32°C) |
| San Antonio | Mar–May, Oct–Nov | Aug (36°C) |
| Charleston | Mar–May, Oct–Nov | Jul (32°C) |
| Savannah | Mar–May, Oct–Nov | Jul (33°C) |
| Fort Lauderdale | Dec–Apr | Aug (30°C) |
| Kauai | Apr–Jun, Sep–Oct | Sep (27°C) |
| Big Island | Apr–Jun, Sep–Oct | Aug (26°C) |
| Sedona | Mar–May, Sep–Nov | Jul (35°C) |
| Boulder | Apr–Jun, Sep–Oct | Jul (33°C) |
Quick answers
What is the best month to visit Boulder?
Apr–Jun, Sep–Oct. May–Jun and Sep–Oct are mild and sunny. Jul–Aug is hot with afternoon storms; Dec–Mar is cold with occasional heavy snow that clears quickly.
When is the rainy season in Boulder?
Rain peaks in May with about 65 mm. No month averages 150 mm or more.
What is the hottest month in Boulder?
July, with average highs of 33°C (91°F).
How cold does Boulder get?
The coolest nights are in December, averaging -6°C (22°F).
More about Boulder
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Sources
- NASA POWER climatology (2001–2020)
- RTD Denver
- City of Boulder
- Denver International Airport
- Boulder Community Health
Climate averages are modelled from NASA POWER (MERRA-2) for 2001–2020 at about 50 km resolution, so coasts and valleys can differ a little. Temperatures are adjusted by 1.1°C for the city's elevation. Compiled and reviewed by SoloSquare. How we compile and score this. Spotted something out of date? Tell us.