Looking Ahead to Winter

 

Average high temperatures in Washington, D.C. range from 75° on October 1 to 64° on Halloween.  However, there have only been six warmer than average days this month in the Nation’s Capital through October 21.  That’s put this month in a strong position to finish as D.C.’s first cooler than average October since 2015.  Average monthly temperatures (combining daily high and low temperatures) in the Nation’s Capital have been 4.7° cooler than average so far this month with near average rainfall. 

Some may wonder if a cooler than average October combined with La Nina conditions is a reliable indicator of what the upcoming winter will be like.  October weather by itself is not a good indicator of the looming winter’s weather.  October 2015, for example, while cooler and drier than average, preceded a warmer than average winter season in the Nation’s Capital.  December 2015 finished as D.C.’s warmest on record and that set the trend for the entire 2015-2016 winter.  Should October 2022 finish as a cooler and wetter than average month, it would be the first such occurrence in the Nation’s Capital since 2011. 

However, the 2015-2016 winter season featured a strong episode of El Nino so the overall weather pattern was a lot different than what NOAA expects for the upcoming 2022-2023 winter season.  NOAA’s Climate Prediction Center released an update on October 13 in which they said there’s a 75% chance La Nina conditions will continue through the 2022-2023 winter season.  The 2011-2012 winter could be a better analog to this autumn since it also featured a moderate episode of La Nina. 

La Nina features the unusual cooling of the waters in the tropical east Pacific Ocean (off the west coast of Mexico).  That’s the opposite of El Nino which features the warming of the waters off the west coast of Mexico.  A La Nina winter in the D.C. Metro Region tends to be warmer and drier than average.  Such was the case during the 2011-2012 winter season when December, January and February saw a combined total of only 2.0” of snow in Washington, D.C.  By comparison, the Nation’s Capital averages 13.7” of annual snowfall according to NOAA. 

The last two winters have also featured moderate intensity La Ninas with below average snowfall in the Nation’s Capital.  There are many factors that go into forecasting seasonal weather, with the presence of La Nina or El Nino being only one, so it isn’t possible to base a seasonal forecast entirely on that.  In any event, this October is well-positioned to finish as D.C. coolest in at least seven years.