September weather forecast
Washington, DC

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Rows of jacaranda trees in spring in the tidal basin of the Washington Monument in Washington city, DC, USA
Rows of jacaranda trees in spring in the tidal basin of the Washington Monument in Washington city, DC, USA

Weather in September

In Washington, D.C., September unveils the first signs of fall with a decrease in temperatures from 61.9°F to 78.4°F. The late summer breezes gradually give way to the crisp wind of the approaching autumn. Sightseeing, picnicking, and waterfront activities continue to allure the city's visitors. But, the declining temperature indicates the need to keep light layers handy for cooler evenings. The seasonal change also contributes to slightly lower relative humidity levels.

Temperature

September's onset in Washington corresponds with a subtle shift in the average high-temperature, slightly moving from 85.8°F in August to a still moderately hot 78.4°F. An average low-temperature of 61.9°F is noted during the nights in September in Washington.

Humidity

In Washington, the average relative humidity in September is 74%.

Rainfall

In Washington, during September, the rain falls for 12.5 days and regularly aggregates up to 1.85" of precipitation. Throughout the year, there are 149.1 rainfall days, and 26.14" of precipitation is accumulated.

Snowfall

April through November are months without snowfall.

Daylight

The average length of the day in September in Washington is 12h and 26min.
On the first day of the month, sunrise is at 6:37 am and sunset at 7:39 pm. On the last day of September, in Washington, sunrise is at 7:03 am and sunset at 6:53 pm EDT.

Sunshine

In September, the average sunshine is 9h.

UV index

In September, the average daily maximum UV index in Washington is 5. A UV Index reading of 3 to 5 represents a moderate threat to health from unprotected exposure to Sun's UV rays for average individuals.
Note: A maximum high UV index of 5 in September translates into the following recommendations:
Take heed. Individuals of lighter complexion can be burned in less than half an hour. Direct exposure to the Sun during its peak hours around mid-day should be minimized for safety. A hat with a generous brim can prevent nearly 50% of UV rays from reaching your eyes.
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FAQ

What is the usual temperature for Washington in September?

In September, in Washington, the average high-temperature is 78.4°F, and the average low-temperature is 61.9°F. The average heat index (a.k.a. 'apparent temperature', 'felt air temperature'), which combines relative humidity and air temperature, in August is evaluated at 95°F.

What is the average humidity in September in Washington?

In September, the average relative humidity in Washington is 74%.

How many days does it rain in September in Washington?

In September, the rain falls for 12.5 days. Throughout September, 1.85" of precipitation is accumulated.

When it does not snow in Washington?

April through November are months without snowfall in Washington, District of Columbia.

What is the average length of the day in September in Washington?

In Washington, the average day length in September is 12h and 26min.

When is the sunrise / sunset in September in Washington?

On the first day of September in Washington, District of Columbia, sunrise is at 6:37 am and sunset at 7:39 pm. On the last day of the month, sunrise is at 7:03 am and sunset at 6:53 pm EDT.

How many hours of sunshine does Washington have in September?

In September, the average sunshine duration in Washington is 9h.

What is the UV index reading in September in Washington?

In Washington, the average daily maximum UV index in September is 5. A UV Index value of 3 to 5 symbolizes a moderate vulnerability from exposure to Sun's UV rays.
Average high temperature
Average low temperature
Average pressure
Average wind speed
Average max. wind speed
Average wind speed gusts
Average humidity
Average rainfall
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Washington, DC

Average temperature in September - Washington, DC
  • Average high temperature in September: 78.4°F

The warmest month (with the highest average high temperature) is July (88°F).
The month with the lowest average high temperature is January (40.6°F).

  • Average low temperature in September: 61.9°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 (27.5°F).

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Average pressure in September
Washington, DC

Average pressure in September - Washington, DC
  • 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).

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Average wind speed in September
Washington, DC

Average wind speed in September - Washington, DC
  • Average wind speed in September: 5.7mph

The windiest month (with the highest average wind speed) is March (7.9mph).
The calmest month (with the lowest average wind speed) is August (5mph).

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Average humidity in September
Washington, DC

Average humidity in September - Washington, DC
  • Average humidity in September: 74%

The month with the highest relative humidity is May (76%).
The months with the lowest relative humidity are April and July (71%).

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Average rainfall in September
Washington, DC

Average rainfall in September - Washington, DC
  • Average rainfall in September: 1.85"

The wettest month (with the highest rainfall) is August (3.46").
The driest month (with the least rainfall) is January (1.57").

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Average rainfall days in September
Washington, DC

Average rainfall days in September - Washington, DC
  • Average rainfall days in September: 12.5 days

The month with the highest number of rainy days is July (16.4 days).
The month with the least rainy days is November (8.1 days).

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Average snowfall in September
Washington, DC

Average snowfall in September - Washington, DC
  • Average snowfall in September: 0"

The month with the highest snowfall is January (2.17").
The months with the least snowfall are April, May, June, July, August, September, October and November (0").

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Average snowfall days in September
Washington, DC

Average snowfall days in September - Washington, DC
  • Average snowfall days in September: 0 days

The months with the highest number of snowfall days are January and February (3.8 days).
The months with the least snowfall days are April, May, June, July, August, September and October (0 days).

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Average daylight in September /
Average sunshine in September
Washington, DC

Average daylight in September / Average sunshine in September - Washington, DC
  • 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 42min).
The months with the least sunshine are January, February and December (Average sunshine: 5h and 6min).

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Average sunshine days in September
Washington, DC

Average sunshine days in September - Washington, DC
  • Average sunshine days in September: 15.7 days

The month with the most sunshine days is November (20 days).
The month with the least sunshine days is May (12.8 days).

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Average UV index in September
Washington, DC

Average UV index in September - Washington, DC
  • Average UV index in September: 5

The month with the highest UV index is June (UV index 7).
The months with the lowest UV index are January and December (UV index 2).

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Average cloud cover in September
Washington, DC

Average cloud cover in September - Washington, DC
  • 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).

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Average visibility in September
Washington, DC

Average visibility in September - Washington, DC
  • 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).

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Washington, District of Columbia, USA

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