Fairfax County (Herndon)
September
Weather in Fairfax County, Virginia for September 2026
Your guide to Fairfax County weather in September - trends and predictions
So far, September 2026 in Fairfax County shows a warmer trend than usual by 2.1 °F.
Expect cooler weather in the next days in Fairfax County with the forecast suggesting a temperature of 26.7 °F, lower than the historical average.
In general, the average temperature in Fairfax County at the beginning of September is 30.9 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 26 °F by the end of September.
The climate of Fairfax County in September is notably wet, with an average of 11 rainy days, and a total of 295.2 mm of precipitation.
New! Chat with our AI weatherman - it’s amazing and free.
Temperatures
Rain 🌧️
More
19
Dry days
11
Rainy days
0
Snow days
26°/17°
Temperatures
13 km/h
Avg max wind
67 %
Avg humidity
Fairfax County Weather September
Move between months or click on a day
Temperatures trend during September in Fairfax County
See the weather trend as well as the moving average line
September weather in Fairfax County day by day
Click on a date for more information
| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Cloudy | 32° /18° | 0 mm | 9 | |
| Sept. 2 | Cloudy | 31° /19° | 3 mm | 8 | |
| Sept. 3 |  Partly cloudy | 31° /19° | 0 mm | 9 | |
| Sept. 4 | Cloudy | 34° /19° | 8.5 mm | 9 | |
| Sept. 5 | Cloudy | 31° /19° | 1.7 mm | 7 | |
| Sept. 6 |  Moderate or heavy rain shower | 30° /19° | 55 mm | 8 | |
| Sept. 7 |  Overcast | 27° /15° | 0 mm | 6 | |
| Sept. 8 |  Sunny | 28° /12° | 0 mm | 8 | |
| Sept. 9 | Partly cloudy | 28° /15° | 0 mm | 6 | |
| Sept. 10 | Overcast | 27° /18° | 1.6 mm | 4 | |
| Sept. 11 | Cloudy | 26° /18° | 0.2 mm | 5 | |
| Sept. 12 | Partly cloudy | 29° /17° | 1.6 mm | 5 | |
| Sept. 13 | Partly cloudy | 29° /19° | 1.6 mm | 5 | |
| Sept. 14 | Cloudy | 28° /18° | 0 mm | 7 | |
| Sept. 15 | Overcast | 27° /16° | 0.8 mm | 7 | |
| Sept. 16 | Sunny | 29° /15° | 0 mm | 6.9 | |
| Sept. 17 | Sunny | 31° /18° | 6.5 mm | 7.2 | |
| Sept. 18 | Overcast | 28° /22° | 1.8 mm | 6.1 | |
| Sept. 19 | Overcast | 25° /20° | 0 mm | 6.7 | |
| Sept. 20 |  Light rain shower | 28° /19° | 2.5 mm | 6 | |
| Sept. 21 | Patchy rain possible | 23° /20° | 0.7 mm | 5 | |
| Sept. 22 | Light rain shower | 25° /21° | 19.9 mm | 6 | |
| Sept. 23 | Light rain shower | 28° /20° | 9.7 mm | 6 | |
| Sept. 24 | Partly cloudy | 28° /18° | 0.4 mm | 7 | |
| Sept. 25 | Sunny | 21° /14° | 0.8 mm | 5 | |
| Sept. 26 | Sunny | 25° /15° | 0 mm | 6 | |
| Sept. 27 | Sunny | 26° /15° | 0 mm | 7 | |
| Sept. 28 | Overcast | 27° /17° | 0 mm | 7 | |
| Sept. 29 | Sunny | 30° /17° | 0 mm | 7 | |
| Sept. 30 | Overcast | 25° /18° | 0 mm | 1 | |
| Next | |||||
Important Notice
Our weather forecast for Fairfax 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 Fairfax County forecast closer to your planned date for the most up-to-date weather information.
Change Month
Fairfax County in September - FAQ
What are the expected maximum and minimum temperatures in Fairfax County during September?
During September, expect a variety of temperatures with highs around 26° and lows near 17°, suitable for diverse activities and preferences.
How much rainfall should be expected in Fairfax County during September?
Significant rainfall exceeding 295.2 mm is expected in Fairfax County during September, occurring over more than 11 days. Preparing for wet conditions is recommended in your planning.
What are the typical wind conditions in Fairfax County during September?
The average wind speed in Fairfax County during September is 13 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Fairfax County
Explore the daily rainfall trends and prepare for Fairfax Countys September weather 💧
Typically, Fairfax County has 11 rainy days in September with a total of 295.2 mm of rainfall.
UV exposure in Fairfax County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
Top locations in Fairfax County
Select a location for an accurate weather forecast
More Locations Quick links
More Fairfax County weather pages
You are here
Where is Fairfax County?Get accurate weather forecasts for Fairfax County, located at latitude 38.97 and longitude -77.386. Stay updated with localized weather information tailored for Fairfax County.
Found a mistake?
We appreciate your attention to details. Tell us here.