Washington, D.C. weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Good
Best time to visit: April – June, September – October
What is the weather like in Washington, D.C. in September?
In September, Washington, D.C. is warm: daytime highs average 26 °C, and nights cool down to about 17 °C. The sea averages 23.7 °C – pleasant for swimming. Expect around 6 hours of sunshine a day. Rain is frequent, with about 10 rainy days and 106 mm in total. All in all, September is a good month for a holiday in Washington, D.C..
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 63 | 78 | 81 |
| Day | 30° | 26° | 20° |
| Night | 21° | 17° | 11° |
| Sea | 26° | 24° | 19° |
| Sun | 7 h | 6 h | 6 h |
| Rain days | 10 | 10 | 8 |
More details for September
- Daylight
- 12 h 30 min06:48 – 19:19
- UV index
- 7 · highclear sky, noon (estimate)All months
- Muggy days
- 9 daysdew point 18 °C or moreAll months
- Wind
- 13 km/haverage daily peakAll months
- Cloud cover
- 54 %on averageAll months
- Hot days
- 5 days30 °C or moreAll months
- Snow days
- 0 days1 cm or more of fresh snowAll months
- Time zone
- UTC−4America/New_York
How the score comes together
- Temperatureweight 50 %100 %
- Sunshineweight 20 %48 %
- Few rainy daysweight 30 %60 %
Each factor is rated from 0 to 100 % and weighted for the travel style “City break”.
What to pack in September
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
- Rain jacket or umbrella
Washington, D.C. in September: quick answers
Is Washington, D.C. hot in September?
Warm rather than hot: in September, daytime highs in Washington, D.C. average 26 °C and nights cool to about 17 °C. On about 5 days the thermometer climbs to 30 °C or more.
Can you swim in Washington, D.C. in September?
Yes. In September the sea averages 23.7 °C – pleasant for swimming.
Does it rain much in Washington, D.C. in September?
Rain is frequent, with about 10 rainy days and 106 mm in total.
Washington, D.C. month by month
The whole year in Washington, D.C.All destinations: USAWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences