WASHINGTON — The first full week of September brought record-setting warmth to the nation’s capital and much of the eastern United States. DC's hottest temperatures of the summer occurred in September, for the first time since 1970.
Friday was the sixth and final day of 90-degree heat in the nation’s capital before temperatures moderated to the 80s today. Three of the six 90-degree days at National Airport produced record highs. The hottest day in the nation’s capital occurred on Tuesday, with a record-setting high of 99 degrees. That broke the standing record of 97 degrees, which occurred back in 1881 according to the National Weather Service.
The last time DC had a high of 99 degrees was back in June of 2022. This was also DC’s hottest September temperature since September 24, 2010, that was also 99 degrees. The nation’s capital has experienced triple-digit September heat only four times since weather records began in 1871. However, none has occurred since September 2, 1980.
Dulles Airport also saw multiple record highs this week with its first 100-degree September day on Wednesday. Weather records date back to 1960 at Dulles. The 100-degree temperature at Dulles followed three consecutive days of 99-degree heat. BWI also experienced 100-degree heat on Wednesday. That was BWI's first occurrence of triple-digit September heat since 1983.
This week’s weather pattern in the nation’s capital was more characteristic of July heat than September's more typical early-fall weather. DC’s six-day stretch in the 90s this week already exceeded the September average of 3-4 such days, according to NOAA.
Despite the historic heat for the first week of September, it’s too early to say whether this month will finish among DC’s warmest. We know that DC’s last day of 90-degree heat for the year typically occurs during the second week of September. That could be the case this year as NOAA’s Climate Prediction Center expects near-to-below average temperatures in the nation’s capital for the next 7 – 14 days.
DC’s final 90-degree day of 2022 occurred on September 4, but the latest in the year it has been 90-degrees in the nation’s capital was October 11, 1919.