How does DC’s September weather stand out?

 

A September day on the grounds of the National Cathedral

This month has become DC’s first wetter than average September since 2021. It will also finish more than a degree warmer than average. However, that obscures how changeable this month’s weather has been in the nation’s capital. 

Ten of the first 13 days of September were warmer than average in Washington, D.C. That includes highs in the 90s on the first four days of the month. September hadn’t had such a hot start to September since 2015. Although not quite record-setting, DC’s high of 98° on September 1 was DC’s hottest September temperature since it was 99° on September 5, 2023.

As hot as much of the first half of September was, the DMV (DC, Maryland and Virginia) saw a major shift in the weather pattern during the second half of the month. Washingtonians experienced eight consecutive cooler than average days through September 28. Measurable rainfall occurred on five of those eight days.

The nation’s capital will finish September 2026 with 4.26” of rain, compared to DC’s average of 3.93”. The wettest day was September 3 with 1.25” at National Airport. Following DC’s wetter than average August (4.27”), this month has given Washingtonians the first instance of consecutive rainier than average months since May and June of 2025.

The most memorable weather event this month was the early season Nor’easter that brought two days of measurable rainfall to the DMV on September 26-27. That also coincided with a stretch of cooler than average temperatures (eight days). Impacts in the DMV weren’t as significant as areas north and east of the nation’s capital, but were still significant. This was a long-lasting event that had far reaching impacts up and down the East Coast of the United States. Nor’easters are relatively rare events in September so it made headlines for a variety of reasons.