September weather forecast
Washington, DC

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

The first month of the autumn, September, is still a warm month in Washington, District of Columbia, with an average temperature varying between 61.9°F (16.6°C) and 78.4°F (25.8°C).

Temperature

In September, the average high-temperature marginally drops from 85.8°F (29.9°C) in August to a still moderately hot 78.4°F (25.8°C). In September, the average low-temperature is 61.9°F (16.6°C).

Humidity

The average relative humidity in September in Washington is 74%.

Rainfall

In September, the rain falls for 12.5 days. Throughout September, 1.85" (47mm) of precipitation is accumulated. In Washington, during the entire year, the rain falls for 149.1 days and collects up to 26.14" (664mm) of precipitation.

Snowfall

April through November are months without snowfall.

Daylight

In September, the average length of the day in Washington is 12h and 26min.
On the first day of September, sunrise is at 6:37 am and sunset at 7:38 pm. On the last day of the month, sunrise is at 7:03 am and sunset at 6:52 pm EDT.

Sunshine

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 health hazard from unprotected exposure to Sun's UV rays for the ordinary person.
Note: The daily maximum UV index of 5 in September interpret into the following advice:
Take precautions - Protection against sunburn is recommended. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
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FAQ

What is the average humidity in September in Washington?

The average relative humidity in September in Washington is 74%.

How much does it rain in Washington in September?

In Washington, in September, it is raining for 12.5 days, with typically 1.85" (47mm) of accumulated precipitation.

When it does not snow in Washington?

In Washington, snow does not fall in April through November.

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

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

When is the sunrise / sunset in September in Washington?

On the first day of September in Washington, sunrise is at 6:37 am and sunset at 7:38 pm. On the last day of the month, sunrise is at 7:03 am and sunset at 6:52 pm EDT.

How many hours of sunshine does Washington have in September?

In September, the average sunshine duration is 9h.

How high is the UV index in September in Washington?

In September, the average daily maximum UV index is 5. A UV Index reading of 3 to 5 represents a medium health risk from unprotected exposure to UV radiation.

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 26min

The month with the longest days is June (Average daylight: 14h and 51min).
The month with the shortest days is December (Average daylight: 9h and 29min).

  • Average sunshine in September: 9h

The month with the most sunshine is July (Average sunshine: 10.7h).
The months with the least sunshine are January, February and December (Average sunshine: 5.1).

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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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