September weather forecastManassas, VA
September
Weather in September
September sees Manassas transitioning into autumn, with gradual cooling temperatures painting a stark contrast to the preceding summer months. The city oversees a notable drop in the average high temperature, descending to 79°F (26.1°C). Drops in temperatures, coupled with diminishing daylight hours, indicate the arrival of fall. Showers become less frequent as the city transitions from the summer-monsoonal patterns. The clear autumnal skies and the mild breeze make September a favorite among many residents, as the sweltering heat gives way to pleasing temperatures.Temperature
A subtle shift in Manassas's weather is observed as August turns into September, with the average high temperature reducing from 85.8°F (29.9°C) to a still warm 79°F (26.1°C). During September, Manassas records a consistent average nighttime temperature of 59.7°F (15.4°C).Humidity
In September, the average relative humidity in Manassas is 76%.Rainfall
The month with the least rainfall in Manassas is September, when the rain falls for 12.7 days and typically collects 1.93" (49mm) of precipitation.Snowfall
May through October are months without snowfall.Daylight
In September, the average length of the day in Manassas, Virginia, is 12h and 26min.On the first day of September in Manassas, sunrise is at 6:39 am and sunset at 7:39 pm. On the last day of the month, sunrise is at 7:05 am and sunset at 6:53 pm EDT.
Sunshine
In Manassas, the average sunshine in September is 8.7h.UV index
In September, the average daily maximum UV index in Manassas is 5. A UV Index estimate of 3 to 5 represents a moderate health risk from unsafe exposure to UV radiation for the average person.Note: A maximum high UV index of 5 in September translates into the following recommendations:
Adopt protective measures - Suggestions to resist sunburn are offered. When the Sun's UV radiation is most intense during midday, it's best to find shade and limit exposure. Sunglasses that ward off UVA and UVB rays play a pivotal role in reducing solar eye damage.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Manassas, VA
- Average high temperature in September: 79°F
The warmest month (with the highest average high temperature) is July (88.3°F).
The month with the lowest average high temperature is January (40.6°F).
- Average low temperature in September: 59.7°F
The month with the highest average low temperature is July (67.1°F).
The coldest month (with the lowest average low temperature) is January (26.4°F).
Average pressure in September
Manassas, 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
Manassas, VA
- Average wind speed in September: 5.1mph
The windiest months (with the highest average wind speed) are March and April (7mph).
The calmest month (with the lowest average wind speed) is August (4.6mph).
Average humidity in September
Manassas, VA
- Average humidity in September: 76%
The month with the highest relative humidity is December (78%).
The month with the lowest relative humidity is July (72%).
Average rainfall in September
Manassas, VA
- Average rainfall in September: 1.93"
The wettest month (with the highest rainfall) is August (3.43").
The driest month (with the least rainfall) is September (1.93").
Average rainfall days in September
Manassas, VA
- Average rainfall days in September: 12.7 days
The month with the highest number of rainy days is May (17.4 days).
The month with the least rainy days is November (9.3 days).
Average snowfall in September
Manassas, VA
- Average snowfall in September: 0"
The month with the highest snowfall is January (3.7").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Manassas, VA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (5.2 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
Manassas, 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: 8h and 42min
The month with the most sunshine is July (Average sunshine: 10h and 42min).
The months with the least sunshine are January, February and December (Average sunshine: 5h and 12min).
Average sunshine days in September
Manassas, VA
- Average sunshine days in September: 15.9 days
The month with the most sunshine days is November (19.8 days).
The month with the least sunshine days is May (11.7 days).
Average UV index in September
Manassas, 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
Manassas, VA
- Average cloud cover in September: 38
The month with the most cloud cover is March (Cloud cover 47).
The month with the least cloud cover is July (Cloud cover 31).
Average visibility in September
Manassas, VA
- Average visibility in September: 5mi
The months with the highest visibility are January, February, March, April, June, July, August and November (6mi).
The months with the lowest visibility are May, September, October and December (5mi).
