September 2021 finished as a warmer and wetter than average month in the Nation’s Capital for only the third time in the last decade. There were two 90° days for a second consecutive September, the first time since 2003-2004 that D.C. residents had two or fewer September days in the 90s.
Last month’s weather was streaky in the Nation’s Capital as six of the final eight days were cooler than average. That followed 11 consecutive warmer than average days through September 22. The majority of D.C.’s September rainfall (4.03”) occurred on two days (September 1, September 23), when a combined total of 2.64” was measured at National Airport.
Some of the finest weather of the year occurs in October with plenty of sunshine and comfortable temperatures. Average high/low temperatures fall throughout the month from 74°/56° on October 1, to 64°/46° on October 31. D.C.’s warmest October temperature occurred two years ago today with a high of 98° on October 2, 2019. By comparison, D.C.’s coolest October temperature of 26° occurred more than once, most recently on October 31, 1917. Since 2011, eight of the last 10 October’s have been warmer than average.
Washingtonians average 3.66” of rain in October. That’s based on NOAA’s updated average for the 30-year period of 1991-2020. Previously, October averaged 3.40” of rainfall for the 30-year period of 1981-2010. Some of the heaviest October rainfall in the D.C. Metro Area results from tropical systems such as Tropical Storm Tammy in 2005, which helped make that October D.C.’s wettest on record.
Although rare, snowfall has occurred in the Nation’s Capital during October. The earliest accumulating snowfall was on October 10, 1979 with 0.3”. D.C.’s largest October snowfall remains the 2.0” on October 30, 1925. The most recent October snowfall in Washington, D.C. occurred on October 29, 2011 with a trace (too little to measure). NOAA’s Climate Prediction Center expects this October to be a warmer and drier than average month in the D.C. Metro Area.
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