District of Columbia, USA
Long term weather forecast
Long term weather forecast

September weather forecast and Climate
Washington, DC

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.
  • Average high temperature in September: 26.4°C

Warmest month (with highest average high temperature) is July (31.3°C).
Month with lowest average high temperature is January (6.3°C).

  • Average low temperature in September: 16.9°C

Month with highest average low temperature is July (21.7°C).
Coldest month (with lowest average low temperature) is January (-1.9°C).

  • Average humidity in September: 69.7%

Month with highest relative humidity is September (69.7%).
Month with lowest relative humidity is April (58%).

  • Average rainfall in September: 94.5mm

Wettest month (with highest rainfall) is May (101.3mm).
Driest month (with lowest rainfall) is February (66.5mm).

  • Average rainfall days in September: 8.3 days

Month with highest number of rainy days is May (11.1 days).
Month with lowest number of rainy days is October (7.7 days).

  • Average snowfall in September: 0mm

Month with highest snowfall is February (144.8mm).
Months with lowest snowfall are April, May, June, July, August, September and October (0mm).

  • Average snowfall days in September: 0 days

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

  • Average daylight in September: 12h

Months with longest days are June and July (Average daylight: 15h).
Month with shortest days is December (Average daylight: 9h).

  • Average sunshine in September: 7.5h

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

  • Average UV index in September: 7

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