September weather forecastGreat Falls, VA
September
Weather in September
The first month of the autumn, September, is also a moderately hot month in Great Falls, Virginia, with an average temperature fluctuating between 78.4°F (25.8°C) and 60.8°F (16°C).Temperature
Great Falls's progression into September involves a minor drop in the average high-temperature, slightly receding from 85.6°F (29.8°C) in August to a still moderately hot 78.4°F (25.8°C). Throughout the nights in September, an average low-temperature of 60.8°F (16°C) is noted.Humidity
In September, the average relative humidity in Great Falls is 74%.Rainfall
In Great Falls, in September, during 12.5 rainfall days, 1.93" (49mm) of precipitation is typically accumulated. In Great Falls, during the entire year, the rain falls for 152.8 days and collects up to 27.64" (702mm) of precipitation.Snowfall
In Great Falls, snow does not fall in May through October.Daylight
In September, the average length of the day 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 6:52 pm EDT.
Sunshine
In Great Falls, the average sunshine in September is 8.7h.UV index
In September, the average daily maximum UV index is 5. A UV Index of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for the ordinary person.Note: The average daily UV index of 5 in September transforms into the following instructions:
Preventative actions are necessary - The mandate to avoid skin and eye damage is in place. During midday, the Sun's radiation is strongest, and it's advisable to reduce direct exposure. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Great Falls, VA
- Average high temperature in September: 78.4°F
The warmest month (with the highest average high temperature) is July (87.6°F).
The month with the lowest average high temperature is January (39.7°F).
- Average low temperature in September: 60.8°F
The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (26.4°F).
Average pressure in September
Great Falls, 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
Great Falls, VA
- Average wind speed in September: 5.5mph
The windiest month (with the highest average wind speed) is March (7.7mph).
The calmest month (with the lowest average wind speed) is August (4.9mph).
Average humidity in September
Great Falls, VA
- Average humidity in September: 74%
The months with the highest relative humidity are October and December (76%).
The month with the lowest relative humidity is July (69%).
Average rainfall in September
Great Falls, VA
- Average rainfall in September: 1.93"
The wettest month (with the highest rainfall) is August (3.39").
The driest month (with the least rainfall) is January (1.77").
Average rainfall days in September
Great Falls, VA
- Average rainfall days in September: 12.5 days
The month with the highest number of rainy days is May (16.3 days).
The month with the least rainy days is November (9.3 days).
Average snowfall in September
Great Falls, VA
- Average snowfall in September: 0"
The month with the highest snowfall is January (2.28").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Great Falls, VA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (4.6 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
Great Falls, VA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 54min).
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 0min).
Average sunshine days in September
Great Falls, VA
- Average sunshine days in September: 16.3 days
The month with the most sunshine days is November (19.3 days).
The month with the least sunshine days is May (12.8 days).
Average UV index in September
Great Falls, 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
Great Falls, 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
Great Falls, 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).
