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

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
Stunning reflective view of rows of jacaranda trees in spring in the tidal basin of the Washington Monument in DC
September, the first month of the autumn, in Washington, is also a moderately hot month, with average temperature fluctuating between 78.4°F (25.8°C) and 61.9°F (16.6°C).

Temperature

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

Humidity

In Washington, the average relative humidity is 74%.

Rainfall

In Washington, it is raining for 12.5 days, with typically 1.85" (47mm) of accumulated precipitation. Throughout the year, in Washington, there are 149.1 rainfall days, and 26.14" (664mm) of precipitation is accumulated.

Snowfall

In Washington snow does not fall in April through November.

Daylight

The average length of the day in Washington, District of Columbia, is 12.4h.

Sunshine

In Washington, the average sunshine is 9h.

UV index

The average daily maximum UV index in September is 5. A UV Index value of 3 to 5 symbolizes a moderate threat to health from the exposure to the Sun's UV rays for the ordinary person.
Note: In September, the average maximum UV index of 5 translate into the following recommendations:
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.

What is the temperature in September in Washington?

The average high-temperature, in September, in Washington, is 78.4°F (25.8°C), while the average low-temperature is 61.9°F (16.6°C).

What is the average humidity in September in Washington?

The average relative humidity in September is 74%.

How much does it rain in Washington in September?

In Washington, District of Columbia, in September, during 12.5 rainfall days, 1.85" (47mm) of precipitation is typically accumulated.

When it does not snow in Washington?

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

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

In Washington, the average length of the day in September is 12.4h.

How long on average sun shines in September in Washington?

In Washington, District of Columbia, the average sunshine in September is 9h.

How high is the UV index in September in Washington?

In Washington, the average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a moderate vulnerability from unsafe exposure to the Sun's UV rays.
Average temperature in September - Washington, DC
  • Average high temperature in September: 25.8°C

The warmest month (with the highest average high temperature) is July (31.1°C).
The month with the lowest average high temperature is January (4.8°C).

  • Average low temperature in September: 16.6°C

The month with the highest average low temperature is July (20.6°C).
The coldest month (with the lowest average low temperature) is January (-2.5°C).

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

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

Average rainfall in September - Washington, DC
  • Average rainfall in September: 47mm

The wettest month (with the highest rainfall) is August (88mm).
The driest month (with the lowest rainfall) is January (40mm).

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 lowest number of rainy days is November (8.1 days).

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

The month with the highest snowfall is January (55mm).
Months with the lowest snowfall are April, May, June, July, August, September, October and November (0mm).

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

Months with the highest number of snowfall days are January and February (3.8 days).
Months with the lowest number of snowfall days are April, 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: 9h

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

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).
Months with the lowest UV index are January and December (UV index 2).