Boulder County (Boulder)
September
Weather in Boulder County, Colorado for September 2027
Your guide to Boulder County weather in September - trends and predictions
In general, the average temperature in Boulder County 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 County 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 County? check out the best time to travel to Boulder County page.
✨ Is September a good time to visit Boulder County? – 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 County Weather September
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Temperatures trend during September in Boulder County
See the weather trend as well as the moving average line
September weather in Boulder County 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 County 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 County forecast closer to your planned date for the most up-to-date weather information.
Change Month
Boulder County in September - FAQ
What are the expected maximum and minimum temperatures in Boulder County 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 County during September?
In September, Boulder County 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 County during September?
The average wind speed in Boulder County during September is 17 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Boulder County
Explore the daily rainfall trends and prepare for Boulder Countys September weather 💧
Typically, Boulder County has 7 rainy days in September with a total of 47 mm of rainfall.
UV exposure in Boulder County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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