Are You Ready for Fall?

Fall arrives in September

Although today is the first day of meteorological fall, this week’s weather pattern will be very summer-like across much of the country with the jet stream far to the north across the eastern United States.  That will allow hazy, hot and humid conditions (more characteristic of late July than early September) to permeate the Mid-Atlantic Region for the next few days.  That’s not unprecedented, though, and many longtime Washingtonians know the first half of September can sometimes feature very hot and humid weather.  

The rainy weather that made this June the second wettest on record in the Nation’s Capital continued through July 13, with more than 15” of rain.  However, since July 14, only a scant 2.68” of rain has fallen.  August was significantly drier than average, with only 1.16” (the driest August since 2006 in Washington, D.C.).  The Mid-Atlantic Region had high pressure in control of the weather which suppressed any significant rainfall for much of the month. 

By comparison, cities in the Southeast like Tampa, Florida, have had one of their wettest summers on record, including the third wettest August with 16.47” of rain and 28.31” of rain for the July-August period (more than 13” above normal).  Florida and much of the southeastern United States had prodigious rainfall the last few days from the remnants of Tropical Storm Erika, but the DC Metro Region didn’t see any.

Now that September has arrived, it’s a good time to discuss what kind of weather September typically features in the Nation’s Capital.  Average temperatures will continue their downward trend with an average high of 84 degrees on September 1 at National Airport, but that falls to 74 degrees by September 30.  September can be quite hot like last September which saw six days at least 90 degrees or hotter and finished 2.8 degrees warmer than average.  September 2014 was also very dry, with only 1.11” of rain at National Airport compared to a September average of 3.72”.  September can also be a rainy month as in 2011 when 8.84” of rain fell in Washington, D.C.

Although there will be a few chances for thunderstorms during the coming week, no widespread heavy rain is on the horizon in the Mid-Atlantic Region.  In fact, today is poised to be the first 90 degree day in the Nation’s Capital since August 24 and will likely be the start of a “heat wave” (at least three consecutive days of at least 90 degrees).  The Nation’s Capital has already had 45 days with temperatures of at least 90 degrees this year – above the annual average of 36 days.  My colleagues and I on the WUSA9 Weather Team will keep you apprised of the latest weather developments as the month of September continues.