A Wild and Unpredictable Autumn

 

September, October and November comprise meteorological fall.  There was no shortage of memorable weather during that three-month period of 2020 in the Nation’s Capital.  It finished as a warmer and wetter than average fall for the second time in three years.  That’s not the only thing 2020 has in common with 2018, DC’s wettest year on record, as 2020 will also finish as one of DC’s Top 10 wettest years on record.

The rainy 2020 fall season got started early with record rainfall on September 10 (2.88”) as part of a two-day rainfall total of 3.52”.  Washingtonians experienced measurable rainfall in September with at least 0.01” of rain on 13 days.  That helped keep temperatures cooler than they otherwise would have been.  An unusually cool air mass also gave residents of the DC Metro Area some of the coolest September weather in nearly a decade, with three consecutive days of highs in the 60s.  The month finished 0.8° cooler than average and 1.81” wetter than average.  That made September 2020 DC’s first cooler and wetter than average September since 2006.

The rainier than average weather continued into October, while milder than average weather also returned to the DC Metro Area.  Measurable rainfall occurred in October with 10 days of at least 0.01” of rain.  DC’s rainiest October weather occurred late in the month with the remnants of Hurricane Zeta, which produced a two-day rainfall total of 2.57” on October 29-30.  October finished 2.4° warmer than average in the Nation’s Capital, which was largely a function of the many warmer than average overnight low temperatures.

November 2020 featured even more extreme weather than September or October.  It finished tied for DC’s fourth warmest November and was DC’s warmest since 2001.  Daily rainfall records were set on both November 11 and November 30 when more than 2” of rain occurred.  That was the first time that the Nation’s Capital had two November days with 2”/+ of rain.  There were severe wind gusts reported in DC’s northern suburbs on November 15 and more severe weather, including two tornadoes in northern Maryland, on November 30. 

Overall, DC’s meteorological fall finished with 16.53” of rain.  That left 2020 tied with 2006 for the seventh wettest autumn.  The five-month period from July 1 – November 30 was so rainy in the DC Metro Area that 2020 will finish as DC’s eighth wettest year, even if no more rain were to occur the rest of December.  That’s despite the below average rainfall that occurred in the Nation’s Capital during four of the first six months of 2020.  Washingtonians tired of the rainy last few months should enjoy the dry weather on tap the rest of the week.