Feeling like fall

 

A cool September morning in Montgomery County, Maryland

The first half of September has featured sunny and stellar fall-like weather in the nation’s capital. It’s also been a cooler and drier than average month so far. Only 0.02” of rain has fallen at National Airport.

Longtime Washingtonians may have noticed the lack of extreme heat over the last few weeks. That’s unlike last September when a six-day heat wave occurred early in the month. There were three consecutive record highs at National Airport from September 4 – 6, 2023. By comparison, this month hasn’t had any 90° heat.

Average daily high temperatures plummet throughout the month in the nation’s capital, from 85° on September 1 to 75° by month’s end. However, the nation’s capital has averaged between three and four days of 90-degree heat over the last 30 years, according to NOAA data. There hasn’t been a September in the nation’s capital without any 90° heat since 2011. 

Five of DC’s 10 warmest September’s have occurred just since 2010. That’s not to say there haven’t been cooler than average stretches of September weather over the last decade, but they have become less frequent than they were over previous decades. For example, from 1999-2011, there were eight September’s without any 90-degree heat in the nation’s capital.

My colleagues and I on the WUSA9 weather team are expecting another cooler than average week with increasing rain chances. That means it’s increasingly likely this September will become DC’s first in over a decade without any 90-degree heat, as well as the first cooler than average month of 2024.