National Harbor Weather in September

September in National Harbor averages 27°C (81°F) during the day and 17°C (63°F) at night. Quite a bit of rainfall is typical this month, with around 101 mm (4 in) on average. An umbrella is a good idea.

Rainfall in National Harbor in September

The climate data from previous years indicates about 9 days of rain, averaging 101 mm (4 in) for the month. Rainfall intensity is on the higher side this month. Expect more substantial showers rather than light, passing rain.

Temperature in National Harbor in September

In September, expect high temperatures in National Harbor, with highs of 27°C (81°F) and lows of 17°C (63°F) at night. This kind of day-to-night contrast is typical for this time of year. Nights cool down to 17°C (63°F), so a light jacket or extra layer is useful once the sun goes down. On the plus side, the cooler nights make for comfortable sleeping conditions.

Sunshine in National Harbor in September

Expect a lot of sunshine this month, with about 225 hours of sun. These sunny conditions add to the overall experience.

Wind Speed in National Harbor in September

Wind speeds average 4 m/s (8 knots) during September. At this speed, expect moderate winds that can raise dust and move small branches. Since this is an average, some days have gentle light winds while others experience stronger breezes that are quite noticeable.

If you prefer dry days with pleasant temperatures, April typically offers the best circumstances. If you're seeking pleasant, dry and sunny weather somewhere else in the world, our weather planner can help you explore other options.