Boulder (CO)
September
Weather in Boulder, Colorado for September 2027
Your guide to Boulder weather in September - trends and predictions
In general, the average temperature in Boulder at the beginning of September is 26.9 °C. As the month progressed, temperatures tended to noticeably cool down, reaching an average of 24 °C by the end of September.
Boulder experiences moderate rainfall in September, with an average of 7 rainy days and a total precipitation of 47 mm.
Is September a good time to visit Boulder? check out the best time to travel to Boulder page.
✨ Is September a good time to visit Boulder? – Ask the AI Weatherman
Temperatures
Rain 🌧️
More
23
Dry days
7
Rainy days
0
Snow days
25°/12°
Temperatures
17 km/h
Avg max wind
42 %
Avg humidity
Boulder Weather September
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Temperatures trend during September in Boulder
See the weather trend as well as the moving average line
September weather in Boulder day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Sunny | 27° /14° | 0.1 mm | 6 | |
| Sept. 2 | Sunny | 27° /14° | 0.1 mm | 8 | |
| Sept. 3 |  Cloudy | 29° /14° | 0 mm | 7 | |
| Sept. 4 |  Light rain | 29° /15° | 3 mm | 8 | |
| Sept. 5 |  Patchy rain possible | 23° /13° | 0.8 mm | 6 | |
| Sept. 6 | Patchy rain possible | 25° /11° | 1 mm | 6 | |
| Sept. 7 | Cloudy | 28° /15° | 0.6 mm | 5 | |
| Sept. 8 |  Partly cloudy | 28° /15° | 0.3 mm | 6 | |
| Sept. 9 | Cloudy | 26° /14° | 0 mm | 7 | |
| Sept. 10 | Light rain | 27° /13° | 4.1 mm | 7 | |
| Sept. 11 | Light rain | 27° /14° | 4.6 mm | 5 | |
| Sept. 12 | Patchy rain possible | 26° /12° | 1.6 mm | 6 | |
| Sept. 13 | Light rain | 25° /12° | 2.7 mm | 6 | |
| Sept. 14 | Patchy rain possible | 27° /12° | 1 mm | 5 | |
| Sept. 15 | Cloudy | 26° /12° | 0.1 mm | 7 | |
| Sept. 16 | Light rain | 24° /11° | 3.8 mm | 4 | |
| Sept. 17 |  Overcast | 23° /12° | 0.9 mm | 4 | |
| Sept. 18 | Sunny | 23° /9° | 0.9 mm | 4 | |
| Sept. 19 | Partly cloudy | 25° /10° | 0.8 mm | 6 | |
| Sept. 20 | Cloudy | 24° /11° | 0.4 mm | 6 | |
| Sept. 21 | Light rain | 21° /9° | 5.2 mm | 6 | |
| Sept. 22 |  Moderate rain | 20° /9° | 11.1 mm | 4 | |
| Sept. 23 | Patchy rain possible | 20° /8° | 1.8 mm | 3 | |
| Sept. 24 | Partly cloudy | 20° /10° | 0.8 mm | 4 | |
| Sept. 25 | Sunny | 24° /9° | 0.4 mm | 5 | |
| Sept. 26 | Sunny | 28° /12° | 0 mm | 6 | |
| Sept. 27 | Cloudy | 25° /14° | 0.1 mm | 5 | |
| Sept. 28 | Sunny | 24° /13° | 0.2 mm | 4 | |
| Sept. 29 | Sunny | 24° /12° | 0.1 mm | 5 | |
| Sept. 30 | Cloudy | 23° /12° | 0.4 mm | 4 | |
| Next | |||||
Important Notice
Our weather forecast for Boulder in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Boulder forecast closer to your planned date for the most up-to-date weather information.
Change Month
Boulder in September - FAQ
What are the expected maximum and minimum temperatures in Boulder during September?
Enjoy moderate daytime temperatures of up to 25° and cooler nights around 12°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Boulder during September?
In September, Boulder can expect light to moderate rainfall, totaling 47 mm across approximately 7 days. Occasional showers are possible, and planning ahead for them could be helpful.
What are the typical wind conditions in Boulder during September?
The average wind speed in Boulder during September is 17 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Boulder
Explore the daily rainfall trends and prepare for Boulders September weather 💧
Typically, Boulder has 7 rainy days in September with a total of 47 mm of rainfall.
UV exposure in Boulder during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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