What Can Washingtonians Expect in October?

Where will Hurricane Joaquin track next?  (Source: NOAA)

The last four months has featured highly variable weather in the Nation’s Capital. May and June were among the warmest on record, while June was also the second wettest in Washington, D.C. That rainy trend continued through the first half of July, but since then there has been significantly below average rainfall.  From August 1 through September 28, there was a rainfall deficit of more than four inches in the Nation’s Capital.

This week, the pendulum has swung the other way to a very rainy weather pattern for much of the eastern United States. Widespread rainfall totals of more than an inch across the Mid-Atlantic Region occurred September 29.  That kept September 2015 from being among the driest on record, but September finished with an average temperature (combing daily highs and lows) of 74.9 degrees that made it the 7^th warmest on record in Washington, D.C.

Longtime Washingtonians will remember how quickly the weather pattern can change from being very dry to wetter-than-average.  September 2005 was the driest on record in the Nation’s Capital with only 0.11” of rain (compared to an average of 3.72”).  It was followed by the wettest October on record with a monthly total of 9.41”.

According to the National Weather Service, the average high temperature on October 1 in Washington, D.C. is 74 degrees, but that falls to 64 degrees by Halloween. October averages 3.4” of rain in the Nation’s Capital and has seen a trace of snow as recently as October 29, 2011!  Although uncommon, 90 degree heat has occurred in early October as recently as in 2013, when it was 91 degrees at National Airport on October 6^th.

October can also see prolific rainfall and flooding from the remnants of a tropical system. The remnants of Hurricane Opal brought the Mid-Atlantic Region appreciable rainfall and some weak tornadoes in early October 1995.  The rainy weather pattern we’re currently in will continue into the weekend.  The track of Hurricane Joaquin looms large over the forecast for the DC Metro Region and much of the eastern United States. 

Joaquin is currently a Category 4 hurricane near the Bahamas and could impact the eastern United States over the weekend and early next week.  The prospect of a tropical storm or hurricane in this part of the country will remind longtime Washingtonians of past storms like Floyd in 1999, Isabel in 2003 and Irene in 2011.  However, there is still a great detail of uncertainty in the track, timing and intensity of the storm. My colleagues and I on the WUSA9 weather team will keep you posted.