Fall has Finally Arrived

NOAA expects cooler than average temperatures to linger in the Mid-Atlantic

Although fall officially arrived last month, September 2018 certainly didn’t feel like autumn.  Last month was one of DC’s warmest September’s on record and finished tied with 2010 for fifth warmest.  September’s warm weather lingered into October, with D.C.’s first 90° October day (October 4) since 2013.  Moreover, the first 12 days of October were the warmest on record with an average temperature (combining daily high and low temperatures) of 74.7° according to the National Weather Service.

However, a major shift in the weather pattern occurred with the arrival of a cold front on three days ago.  The combination of the cold front and the remnants of Hurricane Michael brought a total of 1.51” of rain to the Nation’s Capital on October 11.  Area residents know that September 2018 was a very wet month (D.C.’s fifth wettest on record) with measurable rainfall on eight of its final 10 days.  By comparison, the precipitation on October 11 was D.C.’s first day with measurable rainfall since September 28.

In fact, 2018 has been a very wet year in the Nation’s Capital, with a total of 51.36” of rain since January 1 (compared to the annual average of 39.74”).  January and March were each drier than average this year, so had even average rainfall occurred in those months, DC would be closer to setting a record for wettest year (1889 is the current record-holder for D.C.’s wettest year with 61.33”).  Merely having average rainfall the rest of the year would give DC a total of 59.43”, making 2018 DC’s fourth wettest year on record.  

The warm and dry start to October has come to an end.  That’s because a shift in the jet stream has enabled cooler, fall-like temperatures to take control of the weather pattern for much of the eastern United States.  Temperatures this weekend have been cooler than average.  Average high temperatures in the Nation’s Capital in mid-October are in the upper 60s.  DC’s high and low temperature of 62°/49° on October 13 was the coolest day in the Nation’s Capital since April 29 (58°/49°).  Today’s high/low temperature of 60°/48° was actually more characteristic of early November than mid-October.

NOAA expects cooler than average temperatures to continue through the remainder of the month.  However, given the record warm start to October, having cooler than average temperatures over the second half of the month should help October finish with near average monthly temperatures.