Last updated: June 24, 2025
In September, the average temperature in Fairfax, United States is a delightful 24°C (76°F), making it a perfect time to explore. However, be prepared for a range, as temperatures can dip to a cool 6°C (44°F) or soar to a scorching 37°C (99°F). With an average humidity of 67%, the weather can feel quite humid, and you might encounter 88 mm (3.4 in) of precipitation spread over 7 days. Whether you’re embracing the heat or cooling off in the rain, Fairfax offers a vibrant experience in September!
In September in Fairfax, the average temperature is 24°C (76°F). Maximum temperatures can reach 37°C (99°F), while minimums can drop to as low as 6°C (44°F). It's advisable to pack both light clothing for the warm days and some warmer layers for the cooler nights during your travels.
In Fairfax in September, the precipitation amount is 88 mm (3.4 in) over the course of 7 days.
In Fairfax in September humidity is 67%. With an average temperature of 24°C (76°F), this humidity feels like a warm, steamy embrace, making travel slightly more challenging as you navigate through the thick air.
In Fairfax in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Fairfax.
UV Risk Categories
Weather in Fairfax varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Fairfax, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 3°C (38°F) | 57 mm (2.3 inches) | 77% | moderate |
| February Weather | 4°C (39°F) | 43 mm (1.7 inches) | 76% | high |
| March Weather | 11°C (52°F) | 97 mm (3.8 inches) | 71% | high |
| April Weather | 15°C (59°F) | 104 mm (4.1 inches) | 73% | very high |
| May Weather | 20°C (69°F) | 160 mm (6.3 inches) | 83% | very high |
| June Weather | 26°C (79°F) | 101 mm (4.0 inches) | 83% | extreme |
| July Weather | 28°C (82°F) | 80 mm (3.2 inches) | 81% | extreme |
| August Weather | 27°C (80°F) | 103 mm (4.1 inches) | 73% | very high |
| September Weather | 24°C (76°F) | 88 mm (3.4 inches) | 67% | very high |
| October Weather | 16°C (61°F) | 121 mm (4.8 inches) | 72% | high |
| November Weather | 9°C (49°F) | 34 mm (1.3 inches) | 82% | moderate |
| December Weather | 6°C (43°F) | 35 mm (1.4 inches) | 85% | moderate |