September weather forecastMcLean, VA
September
Weather in September
The first month of the autumn, September, is still a warm month in McLean, Virginia, with temperature in the range of an average high of 78.6°F (25.9°C) and an average low of 61.2°F (16.2°C).Temperature
With September's onset, the weather reveals a slight temperature decrease, transitioning from 85.6°F (29.8°C) in August to a still moderately hot 78.6°F (25.9°C). During September, McLean experiences an average low-temperature of 61.2°F (16.2°C) at night.Humidity
The average relative humidity in September 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
In McLean, 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 September, the average sunshine in McLean, Virginia, is 9h.UV index
The average daily maximum UV index in September is 5. A UV Index value of 3 to 5 symbolizes a medium health hazard from exposure to the Sun's UV rays for ordinary individuals.Note: A maximum daily UV index of 5 during September morphs into the following directions:
Be vigilant - A duty to shield skin and eyes from injury exists. Considering the Sun's intensity during midday, it's wise to minimize direct exposure. Enhance your sun protection with tightly woven, yet airy clothing.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
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
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
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
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
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
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
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
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
McLean, 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: 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
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
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
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
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).
