easeweather.com
Units
°C
°F
Boulder County
Forecast Today Tomorrow
more
Colorado United States

Weather in Boulder County for September 2025

Your guide to Boulder County weather in September - trends and predictions

    Temperatures

  • In general, the average temperature in Boulder County at the beginning of September is 26.3 °F. As the month progressed, temperatures tended to moderately rise, reaching an average of 27.9 °F by the end of September.

  • Rain 🌧️

  • With an average of 5 rainy days, Boulder County experiences minimal rainfall in September.

  • More

  • New! Chat with our AI weatherman - it’s amazing and free.

Average dry days
25
Dry days
Average rainy days
5
Rainy days
Average snowy days
0
Snow days
Average temperatures
26°/12°
Temperatures
Average wind speed
17 km/h
Avg max wind
Average humidity
36 %
Avg humidity

Boulder County Weather September

Move between months or click on a day
Select a date

You can click on date

Access Boulder County weather forecasts with a simple click. Select any date for comprehensive insights on temperature, rainfall, and wind conditions.
Got it

Temperatures trend during September in Boulder County

See the weather trend as well as the moving average line

September weather day by day

Click on a date for more information
Date Weather Temperatures Rain UV More
Sept. 1 Sunny
Sunny
28° /14° 0 mm 7
Sept. 2 Cloudy
Cloudy
28° /14° 0 mm 6
Sept. 3 Cloudy
Cloudy
30° /15° 0 mm 7
Sept. 4 Moderate or heavy rain shower
Moderate or heavy rain shower
26° /14° 9.1 mm 6
Sept. 5 Patchy rain possible
Patchy rain possible
21° /13° 2.3 mm 5
Sept. 6 Sunny
Sunny
25° /11° 0 mm 7
Sept. 7 Cloudy
Cloudy
26° /13° 0 mm 6
Sept. 8 Partly cloudy
Partly cloudy
28° /14° 0 mm 7
Sept. 9 Cloudy
Cloudy
28° /16° 0 mm 6
Sept. 10 Overcast
Overcast
27° /16° 0 mm 6
Sept. 11 Moderate or heavy rain shower
Moderate or heavy rain shower
25° /14° 3.3 mm 6
Sept. 12 Partly cloudy
Partly cloudy
29° /12° 0 mm 7
Sept. 13 Partly cloudy
Partly cloudy
23° /11° 0 mm 6
Sept. 14 Sunny
Sunny
27° /12° 0 mm 7
Sept. 15 Cloudy
Cloudy
27° /13° 0 mm 6
Sept. 16 Overcast
Overcast
26° /13° 0 mm 6
Sept. 17 Overcast
Overcast
27° /12° 0 mm 6
Sept. 18 Sunny
Sunny
25° /8° 0 mm 7
Sept. 19 Partly cloudy
Partly cloudy
25° /11° 0 mm 7
Sept. 20 Cloudy
Cloudy
27° /13° 0 mm 6
Sept. 21 Heavy rain at times
Heavy rain at times
17° /10° 15.3 mm 4
Sept. 22 Moderate or heavy rain shower
Moderate or heavy rain shower
12° /6° 31.1 mm 3
Sept. 23 Cloudy
Cloudy
23° /7° 0 mm 5
Sept. 24 Partly cloudy
Partly cloudy
21° /10° 0 mm 6
Sept. 25 Sunny
Sunny
28° /11° 0 mm 7
Sept. 26 Sunny
Sunny
31° /14° 0 mm 8
Sept. 27 Cloudy
Cloudy
28° /16° 0 mm 6
Sept. 28 Sunny
Sunny
29° /14° 0 mm 7
Sept. 29 Sunny
Sunny
30° /14° 0 mm 8
Sept. 30 Cloudy
Cloudy
28° /12° 0 mm 6
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.

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 26° 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?
Moderate rainfall is anticipated in Boulder County during September, with a total of 61.2 mm spread over approximately 5 days. Considering plans for rainy days is advisable.
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 💧

UV exposure in Boulder County during September

Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
Top locations in Boulder County
Select a location for an accurate weather forecast
More Locations

Quick links

Location coordinates Where is Boulder County?

Get accurate weather forecasts for Boulder County, located at latitude 40.015 and longitude -105.271. Stay updated with localized weather information tailored for Boulder County.

Found a mistake?
We appreciate your attention to details. Tell us here.