September weather forecast and climate
Washington, DC

Stunning reflective view of rows of jacaranda trees in spring in the tidal basin of the Washington monument in DC, USA
Stunning reflective view of rows of jacaranda trees in spring in the tidal basin of the Washington monument in DC, USA
Fall weather brings the average daily temperatures in the range of a comfortable 63°F (17.2°C) to 79°F (26.1°C).
September is one of the best intervals to visit Washington, D.C., with fewer crowds compared to spring and summer due to the end of the school breaks. There are fewer lines to stand in, and more time to enjoy the tours in the lovely autumn. Be sure to pack some warm clothes to protect from an odd cold bout or two. The Library of Congress National Book Festival during September is also an entertaining way to pass rainy fall afternoons.

What is the temperature in September in Washington?

The average high-temperature, in September, in Washington, is 79.5°F (26.4°C), while the average low-temperature is 62.4°F (16.9°C).

How much does it rain in Washington in September?

In September, in Washington, the rain falls for 8.3 days. Throughout September, 3.7" (94.5mm) of precipitation is accumulated.
Average temperature in September - Washington, DC
  • Average high temperature in September: 79.5°F

The warmest month (with the highest average high temperature) is July (88.4°F).
The month with the lowest average high temperature is January (43.4°F).

  • Average low temperature in September: 62.4°F

The month with the highest average low temperature is July (71.1°F).
The coldest month (with the lowest average low temperature) is January (28.6°F).

Average humidity in September - Washington, DC
  • Average humidity in September: 69.7%

The month with the highest relative humidity is September (69.7%).
The month with the lowest relative humidity is April (58%).

Average rainfall in September - Washington, DC
  • Average rainfall in September: 3.7"

The wettest month (with the highest rainfall) is May (4").
The driest month (with the lowest rainfall) is February (2.6").

Average rainfall days in September - Washington, DC
  • Average rainfall days in September: 8.3 days

The month with the highest number of rainy days is May (11.1 days).
The month with the lowest number of rainy days is October (7.7 days).

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

The month with the highest snowfall is February (5.7").
Months with the lowest snowfall are April, May, June, July, August, September and October (0").

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

The month with the highest number of snowfall days is January (3 days).
Months with the lowest number of snowfall days are May, June, July, August, September and October (0 days).

Average daylight in September / Average sunshine in September - Washington, DC
  • Average daylight in September: 12.4h

The month with the longest days is June (Average daylight: 14.9h).
The month with shortest days is December (Average daylight: 9.5h).

  • Average sunshine in September: 7.5h

The month with most sunshine is June (Average sunshine: 9.4h).
The month with least sunshine is December (Average sunshine: 4.3h).

Average UV index in September - Washington, DC
  • Average UV index in September: 7

Months with the highest UV index are June and July (UV index 9).
Months with the lowest UV index are January and December (UV index 2).

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