Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
September's onset introduces a mild reduction in the average high-temperature, from a warm 85.6°F (29.8°C) in August to a still moderately hot 78.6°F (25.9°C). During September, West McLean records an average temperature of 61.2°F (16.2°C) at night.Humidity
In September, the average relative humidity is 74%.Rainfall
January and September are months with the least rain when the rain falls for 8.1 days and typically aggregates up to 0.51" (13mm) of rain.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 the month, sunrise is at 6:38 am and sunset at 7:38 pm. On the last day of September, sunrise is at 7:04 am and sunset at 6:52 pm EDT.
Sunshine
In West McLean, the average sunshine in September is 9h.UV index
The average daily maximum UV index in September is 5. A UV Index estimate of 3 to 5 represents a medium vulnerability from unsafe exposure to UV radiation for the average person.Note: A daily maximum UV index of 5 in September translates into the following instructions:
Guard yourself - Avoiding sunburn is suggested. It's recommended to limit sun exposure when its radiation is at its peak during midday. For effective sun eye protection, rely on sunglasses certified for UVA and UVB resistance.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the temperature in September?
What is the average humidity in September?
What is the driest month?
How much does it rain in September?
When it does not snow?
How many hours of daylight does West McLean have in September?
What time are sunrise and sunset in September?
How many hours of sunshine does West McLean have in September?
How high is the UV index in September?
Average temperature in September
West McLean, VA
- Average high temperature in September: 78.6°F
The warmest month (with the highest average high temperature) is July (87.4°F).
The month with the lowest average high temperature is January (40.1°F).
- Average low temperature in September: 61.2°F
The month with the highest average low temperature is July (69.1°F).
The coldest month (with the lowest average low temperature) is January (26.8°F).
Average pressure in September
West McLean, 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
West McLean, 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
West McLean, 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 (70%).
Average rainfall in September
West McLean, VA
- Average rainfall in September: 0.51"
The wettest month (with the highest rainfall) is August (1.5").
The driest months (with the least rainfall) are January and September (0.51").
Average rainfall days in September
West McLean, VA
- Average rainfall days in September: 8.1 days
The month with the highest number of rainy days is July (13.5 days).
The month with the least rainy days is November (5.6 days).
Average snowfall in September
West McLean, VA
- Average snowfall in September: 0"
The month with the highest snowfall is January (0.98").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
West McLean, VA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (3.6 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
West McLean, VA
- Average daylight in September: 12h and 2min
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: 9h and 0min
The month with the most sunshine is July (Average sunshine: 10h and 54min).
The months with the least sunshine are February and December (Average sunshine: 5h and 6min).
Average sunshine days in September
West McLean, VA
- Average sunshine days in September: 19.1 days
The month with the most sunshine days is November (23 days).
The month with the least sunshine days is July (14.3 days).
Average UV index in September
West McLean, 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, November and December (UV index 2).
Average cloud cover in September
West McLean, VA
- Average cloud cover in September: 36
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
West McLean, 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).
West McLean, Virginia, USA
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