Boulder Weather in September

September in Boulder typically sees daytime highs of 26°C (79°F) and nighttime lows of 10°C (50°F). Rainfall is also possible this month, so it's worth packing an umbrella.

Rainfall in Boulder in September

Typically, you can expect about 8 days of rain this month, with 67 mm (2.6 in) on average. Rainfall intensity is on the higher side this month. Expect more substantial showers rather than light, passing rain.

Temperature in Boulder in September

Boulder in September is worth a visit. The temperature is perfect, with 26°C (79°F) during the day and 10°C (50°F) at night. Conditions stay fairly consistent through the month, making it easier to plan what to wear. With lows around 10°C (50°F), nights are cold. The upside is that cool, crisp nights are often the best for a deep sleep.

Sunshine in Boulder in September

Expect sunny days throughout the month, with an estimated 270 hours of sunshine. This makes it a pleasant time to visit Boulder.

If you're a fan of comfortable temperatures and drier conditions, September is a great time to visit.

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Check the conditions for any month of the year.

• January
• February
• March
• April

• May
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• July
• August

• September
• October
• November
• December

For a detailed overview over the year and the best time to visit the United States of America, check out our Boulder's climate page.

Boulder Temperature in September

Min Temperature 10°C (50°F)  

Max Temperature 26°C (79°F)  

Chance of Rain 27%  

Precipitation 67 mm (2.6 in)  

Rainy days 8 days  

Humidity 50% *  

Sunshine 270 hours *  

Percentage Sunshine 73% *  

* Data from: Denver, the United States of America (45 KM, 28 Miles).

What to Wear in Boulder in September

Warm weather calls for comfortable, breathable clothing in September. Cotton t-shirts, shorts, light dresses, and sandals are perfect. You might still want a light layer for evenings or air-conditioned places (for example buses). Rain is likely on several days, so bring a good rain jacket. You'll definitely want to pack sunglasses and sunscreen. There will be plenty of bright sunshine this month.

What To Do in Boulder in September

We rated the following activities from 1 (least suitable) to 10 (best) to do.

Swimming

9/10

Cycling

8/10

Walking

8/10

Camping

4/10

Outdoor sports

8/10

Select a Month

Check the conditions for any month of the year.

• January
• February
• March
• April

• May
• June
• July
• August

• September
• October
• November
• December

For a detailed overview over the year and the best time to visit the United States of America, check out our Boulder's climate page.

More climate data for Boulder

Temperature Rainfall Sunshine Humidity

See the full Boulder climate overview or explore weather in the United States of America.