What September feels like in Washington DC
For Washington DC, September is early autumn on the calendar. Warm daytime weather invites long lunches outside and evening strolls. After dark the temperature drops clearly: nights stay mild. The air carries some moisture, so hot spells feel a little sticky.
Rain in Washington DC in September
It is a changeable month: rain comes about one day in 3, with dry spells in between. When rain comes it is heavy, about 12.2 mm (0.5 in) per wet day, often in short, strong bursts. That is heavier than Washington DC's usual 9.8 mm per rainy day across the year. It is among the three wettest months of the year.
Daylight and sunshine in September
In mid-September, sunrise is at about 6:48 am and sunset at about 7:19 pm (local time) — 12 h 30 min of daylight. Evenings are drawing in — 1 h 14 min less daylight than mid-August. The sun is out for roughly 72% of those daylight hours, so there are plenty of bright spells.
How September compares to the rest of the year
September is the 4th warmest month of the year in Washington DC. Compared with August, afternoons are 3.6°C (6.5°F) cooler, with 2 mm more rain. Temperatures keep falling into October. By October, typical highs are 20°C (68°F).
Who September suits
- Sightseeing: a good fit — the weather rarely gets in the way of a city walk.
- Parks & outdoor: less ideal — afternoons are too warm to linger outside.
Tips for visiting Washington DC in September
Versatile Layers
Mornings and evenings are cooler than midday, so dress in layers.
Rain Protection
A packable rain jacket saves the day on showery afternoons.
Sunglasses
Frequent sunshine — sunglasses and a light hat.
Quick questions
How warm is Washington DC in September?
Afternoons average 26.1°C (79°F) and nights about 17°C (62.6°F) — warm by most people's standards. It is the 4th warmest month of the year.
Does it rain a lot in Washington DC in September?
Yes, fairly — rain falls about one day in 3 and totals about 122 mm, so an umbrella is worth carrying.
What should I wear in Washington DC in September?
The numbers point to versatile layers, rain protection and sunglasses. Add a layer for after dark.
Is September or October better for visiting Washington DC?
October scores better on our climate ranking (#1 of 12 vs #2), rated Great against Great. October is cooler and has fewer rainy days.