September weather forecastFairfax, VA
September
Weather in September
September announces the onset of fall in Fairfax, Virginia. The transition from August is apparent with diminishing daylight hours, a drop in temperature highs, and a concurrent decrease in the UV index. The month experiences balanced weather conditions in terms of rainfall, sunlight, and relative humidity. September serves as a prelude to the more pronounced autumnal characteristics that take over in October.Temperature
In the transition to September, Fairfax observes a minor drop in the average high-temperature, shifting from 85.8°F (29.9°C) in August to a still warm 78.4°F (25.8°C). In the month of September, Fairfax's average low-temperature falls to a mild 60.6°F (15.9°C).Humidity
In Fairfax, Virginia, the average relative humidity in September is 75%.Rainfall
The month with the least rainfall is September, when the rain falls for 13.1 days and typically collects 2.01" (51mm) of precipitation.Snowfall
May through October are months without snowfall.Daylight
The average length of the day in September is 12h and 26min.On the first day of September, sunrise is at 6:38 am and sunset at 7:39 pm. On the last day of the month, sunrise is at 7:04 am and sunset at 6:53 pm EDT.
Sunshine
In Fairfax, the average sunshine in September is 9h.UV index
In Fairfax, the average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a medium vulnerability from unsafe exposure to UV radiation for average individuals.Note: The UV index of 5 during September translates into the following guidance:
Take necessary precautions - Suggestions to elude sunburn are provided. Avoid the Sun's strongest UV rays by seeking shade and limiting exposure during midday. To cut down UV radiation exposure by about half, sport a wide-brim hat.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Fairfax, VA
- Average high temperature in September: 78.4°F
The warmest month (with the highest average high temperature) is July (88°F).
The month with the lowest average high temperature is January (40.5°F).
- Average low temperature in September: 60.6°F
The month with the highest average low temperature is July (68.4°F).
The coldest month (with the lowest average low temperature) is January (26.4°F).
Average pressure in September
Fairfax, VA
- Average pressure in September: 30.05"Hg
The month with the highest atmospheric pressure is November (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.95"Hg).
Average wind speed in September
Fairfax, VA
- Average wind speed in September: 5.3mph
The windiest month (with the highest average wind speed) is March (7.4mph).
The calmest month (with the lowest average wind speed) is August (4.7mph).
Average humidity in September
Fairfax, VA
- Average humidity in September: 75%
The months with the highest relative humidity are October and December (77%).
The month with the lowest relative humidity is July (71%).
Average rainfall in September
Fairfax, VA
- Average rainfall in September: 2.01"
The wettest month (with the highest rainfall) is August (3.78").
The driest month (with the least rainfall) is September (2.01").
Average rainfall days in September
Fairfax, VA
- Average rainfall days in September: 13.1 days
The months with the highest number of rainy days are May and August (17.3 days).
The month with the least rainy days is November (9.1 days).
Average snowfall in September
Fairfax, VA
- Average snowfall in September: 0"
The month with the highest snowfall is January (3.54").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Fairfax, VA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (5.6 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Fairfax, VA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in September: 9h and 0min
The month with the most sunshine is July (Average sunshine: 10h and 48min).
The months with the least sunshine are January, February and December (Average sunshine: 5h and 12min).
Average sunshine days in September
Fairfax, VA
- Average sunshine days in September: 15.7 days
The month with the most sunshine days is November (19.6 days).
The month with the least sunshine days is July (11.3 days).
Average UV index in September
Fairfax, VA
- Average UV index in September: 5
The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Fairfax, VA
- Average cloud cover in September: 37
The month with the most cloud cover is March (Cloud cover 46).
The month with the least cloud cover is July (Cloud cover 30).
Average visibility in September
Fairfax, VA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is May (5mi).
