How Hot and Dry Can September Be?

Labor Day is great time of year to be outdoors!

Although fall arrives in September, significant summer-like heat often occurs then as well.  There already was one heat wave this month with a four-day stretch of 90 degree days to start the month.  A similar stretch of hot weather is poised to begin today, with a high temperature around 90 degrees this afternoon and even hotter temperatures looming the next few days in the DC Metro Region.

September is a transitional month in the Nation’s Capital with an average high of 84 degrees on September 1, but that falls to 74 degrees by the end of the month.  During the 20-year period from 1994 through 2014, Washingtonians saw an average of 3.4 days of 90 degree heat in September along with one day of at least 95 degrees.  According to the National Weather Service, the hottest temperature on record in the Nation’s Capital during the month of September is 104 degrees on September 7, 1881.

Being the busiest month of the hurricane season, there have also been some wet Septembers in the Nation’s Capital.  Washington, D.C. averages 3.72” of rain in September, but the remnants of Hurricanes Dennis and Floyd helped make 1999 the fourth wettest September on record when 10.27” of rain fell.  In fact, September 1999 was the second wettest on record at National Airport since it opened in 1941 (behind only the 12.36” of rain that occurred in September 1975).  By comparison, September 2005 was the driest on record in the Nation’s Capital when only 0.11” of rain fell.

Although not as dry as the summer of 1995 (when a stretch of 33 consecutive days without measureable rainfall ended on September 9), the DC Metro Region has had significantly below average rainfall since of late.  Since July 14, only 2.68” has fallen at National Airport through yesterday compared to an average of 5.71” for that time.  My colleagues and I on the WUSA9 Weather Team will keep you apprised on the latest weather forecasts, including the prospect of rain later in the week.