Washington, DC weather in September
Washington is warm and often humid in September, with some rain: highs average 81°F and nights drop to about 64°F. Rain falls on about 9 days. A good month for most outdoor plans.
- Normal high
- 81°F
- Normal low
- 64°F
- Wet days
- 9
- 3.9 in total
- Muggy days
- 9
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 85°F | 75°F |
| Normal low | 69°F | 59°F |
| Chance of a wet day | 27% | 28% |
| Sunrise / sunset | 6:37 am / 7:39 pm | 7:03 am / 6:53 pm |
| Daylight | 13.0 h | 11.8 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Eastern Time).
A typical September day
- 6 am65°Fdew point 60°F
- 9 am71°Fdew point 61°F
- Noon77°Fdew point 60°F
- 3 pm79°Fdew point 59°F
- 6 pm75°Fdew point 59°F
- 9 pm71°Fdew point 61°F
NOAA hourly normals (local standard time) from Washington Reagan Airport (3 mi away); average wind 8 mph; clear or few clouds in 48% of daytime hours, mostly cloudy or overcast in 39%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F10 of 30
- Hot dayshigh 90°F or more4 of 30
- Muggy daysdaily mean dew point 65°F or more9 of 30
- Wet daysat least 0.01 in of rain or melted snow9 of 30
- Notable rainat least 0.10 in6 of 30
- Freezing nightslow 32°F or below0 of 30
- Snow on the groundsnow depth 1 in or more0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 3.9 in; a dry September brings about 1.6 in and a wet one about 5.9 in (25th and 75th percentiles). About 3 days bring half an inch or more, and about 1 an inch or more.
How September varies from year to year
- Warmest September, 1991-20202019: average high 86°F
- Coolest September2006: average high 75°F
- Wettest September1999: 10.3 in
- Driest September2005: 0.1 in
- Highest reading99°F (September 24, 2010)
- Lowest reading44°F (September 30, 1992)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 88°F | 81°F | 69°F |
| Normal low | 71°F | 64°F | 52°F |
| Wet days | 9 | 9 | 8 |
| Comfortable days | 1 | 10 | 16 |
| Daylight | 13.6 h | 12.4 h | 11.2 h |
Highs change by -7°F from August and -12°F into October.
Nearby alternatives in September
- Cooler: Frederick, MD41 mi · high 76°F · 9 wet days
How Washington ranks in September
- Normal high188th warmest of 378 cities
- Wet days227th driest of 378
- Comfortable days158th most of 342
What to pack for Washington in September
- A rain jacket or umbrella – rain on about 9 days
Heating and cooling
September has 16 heating degree days and 238 cooling degree days (base 65°F), 5% of the year's total heating and cooling demand.
Questions
How hot is Washington in September?
The normal high is 81°F and the normal low is 64°F. From 1991 to 2020 the hottest September reading was 99°F (September 24, 2010).
Does it rain a lot in Washington in September?
About 9 days in September have at least 0.01 in of precipitation, and the normal total is 3.9 in. The wettest September in 1991-2020 was in 1999 (10.3 in); the driest was in 2005 (0.1 in).
Is September a good time to visit Washington?
September ranks 4th of 12 months on our comfort score for Washington (60 out of 100). It has about 10 comfortable days and about 4 days at 90°F or hotter. The best months are April, May and October.
Where the numbers come from
- Temperature, rain, snowfall, snow depth, frost dates and humidity and wind by hour: Washington Reagan Airport (USW00013743), 3.2 mi S of the city center, 10 ft . NOAA normals and daily records, 1991-2020.
- Cloud cover: Camp Springs Andrews AFB (USW00013705), 11 mi ESE of the city center, 282 ft (258 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Ronald Reagan Washington Natl Airport (724050-13743), 3.3 mi S of the city center, 13 ft . Hourly observations, 1991-2020.