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 is marked by a subtle drop in average high-temperatures, transitioning from a moderately hot 85.6°F (29.8°C) in August to a still warm 78.4°F (25.8°C). Chantilly's nights in September experience an average temperature drop to a moderate 59.9°F (15.5°C).Humidity
In September, the average relative humidity is 75%.Rainfall
September is the month with the least rainfall. Rain falls for 12 days and accumulates 1.89" (48mm) of precipitation.Snowfall
In Chantilly, snow does not fall in May through October.Daylight
In Chantilly, the average length of the day in September is 12h and 26min.On the first day of the month, sunrise is at 6:39 am and sunset at 7:39 pm. On the last day of September, in Chantilly, sunrise is at 7:05 am and sunset at 6:53 pm EDT.
Sunshine
The average sunshine in September in Chantilly is 8.7h.UV index
In Chantilly, the average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from exposure to the Sun's UV radiation for ordinary individuals.Note: The maximum UV index of 4 during September leads to these instructions:
Preventative actions are necessary - Recommendations to ward off sunburn are given. The Sun's most harmful UV rays are emitted around midday; avoid staying outdoors for long during this time. Sunglasses providing both UVA and UVB protection are non-negotiable on sunlit days.
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 many days does it rain in September?
When it does not snow?
What is the average length of the day in September?
What time are sunrise and sunset in September?
How long on average sun shines in September in Chantilly?
What is the UV index intensity in September?
Average temperature in September
Chantilly, VA
- Average high temperature in September: 78.4°F
The warmest month (with the highest average high temperature) is July (88.2°F).
The month with the lowest average high temperature is January (39.7°F).
- Average low temperature in September: 59.9°F
The month with the highest average low temperature is July (67.3°F).
The coldest month (with the lowest average low temperature) is January (25.7°F).
Average pressure in September
Chantilly, 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
Chantilly, VA
- Average wind speed in September: 5.2mph
The windiest months (with the highest average wind speed) are March and April (7.3mph).
The calmest month (with the lowest average wind speed) is August (4.7mph).
Average humidity in September
Chantilly, 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
Chantilly, VA
- Average rainfall in September: 1.89"
The wettest month (with the highest rainfall) is August (3.74").
The driest month (with the least rainfall) is September (1.89").
Average rainfall days in September
Chantilly, VA
- Average rainfall days in September: 12 days
The month with the highest number of rainy days is May (17.5 days).
The month with the least rainy days is November (9.3 days).
Average snowfall in September
Chantilly, VA
- Average snowfall in September: 0"
The month with the highest snowfall is January (3.58").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Chantilly, VA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (5.3 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
Chantilly, 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: 8h and 4min
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 6min).
Average sunshine days in September
Chantilly, VA
- Average sunshine days in September: 17.2 days
The month with the most sunshine days is November (19.6 days).
The month with the least sunshine days is July (12.1 days).
Average UV index in September
Chantilly, VA
- Average UV index in September: 4
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
Chantilly, 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
Chantilly, VA
- Average visibility in September: 6mi
The months with the highest visibility are February, March, April, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January and May (5mi).
Chantilly, Virginia, USA
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