October Weather is Unpredictable

Fall is a fine time of year in the Nation's Capital

Although today was the seventh consecutive day of rain in the Nation’s Capital, September 2016 still finished with below average monthly rainfall (2.5”) for a fourth straight year.  September 2016 also tied with 1930 for being the third warmest on record with a monthly average temperature (combining daily high and low temperatures) of 76 degrees.

October has gotten off to a much chillier start with a high temperature of only 67 degrees yesterday.  That’s in contrast to the average high temperature of 74.  By Halloween, Washington, D.C.’s average high and low temperatures drop to 64 and 46 degrees.  Washington, D.C.’s hottest temperature on record during the month of October is 96 degrees which occurred on October 5, 1941.  By contrast, the coolest temperature during the month of October in the Nation’s Capital is 26 degrees which occurred twice, most recently on October 31, 1917.

October can feature a wide variety of temperatures in the Mid-Atlantic Region.  Although uncommon, 90 degree heat does occur during October, with the last time on October 6, 2013 when it was 91 degrees.  According to the National Weather Service, the latest in the year it’s been at least 90 degrees in Washington, D.C. is October 11.  Severe weather does sometimes occur in October, such as when five tornadoes struck central Virginia on October 13, 2011.  

By comparison, Washington, D.C.’s earliest measureable snowfall of the season (0.3”) occurred on October 10, 1979.  A trace of snow occurred downtown as recently as October 29, 2011 with several inches north and west of town.  The Nation’s Capital averages 3.4” of rain in October, and the wettest October on record was in 2005 with 9.41” of rainfall.  That’s when the remnants of Tropical Storm Tammy impacted the Mid-Atlantic Region. 

October can also be a busy month of the hurricane season.  Several hurricanes have directly or indirectly impacted the Mid-Atlantic Region in October, including Hurricane Hazel in 1954 and the remnants of Hurricane Opal in 1995.  Sandy was a major Category 3 hurricane at peak intensity in late October 2012, but was no longer a tropical system by the time it impacted the Mid-Atlantic and northeastern United States.  The National Hurricane Center officially designated Sandy a “post-tropical cyclone” before it came ashore in New Jersey.  The impact was the same, though, with significant coastal flooding combined with heavy rainfall and high winds well inland.

It’s important to remember the lessons of past October storms like Hazel, Opal and Sandy while powerful Hurricane Matthew is currently in the Caribbean Sea.  Although a great deal of uncertainty exists regarding its future storm track, Matthew is expected to track northward into the southeast Atlantic Ocean near the Bahamas.  Areas up and down the U.S. East Coast need to pay attention to this major hurricane.