Has June 2018 Gotten off to an Unusual Start ?

June 2018 has gotten off to a Wet Start in D.C.  (Source: NOAA)

June has seen a continuation of the wet and warm weather pattern that dominated local headlines over the second half of May.  Washington, D.C. had 11.39” of rain just since May 12.  That’s significant because the Nation’s Capital averages only 10.44” of rain for the entire three-month period of June – August.

Last month was only the second May on record to finish among the 10 wettest and 10 warmest in Washington, D.C.  Such conditions occur more frequently in June.  For example, June 2015 was D.C.’s sixth warmest on record with an average monthly temperature (combining daily high and low temperatures) of 78.1°.  It was also D.C.’s second wettest June with 11.94” at National Airport.  June 2013 was D.C.’s fifth wettest on record with a monthly average temperature of 76.5°.

Being the first month of the hurricane season, June sometimes sees tropical storms and hurricanes.  The remnants of tropical systems can bring the Mid-Atlantic Region significant June rainfall.  Such was the case in June 1972, when the remnants of Hurricane Agnes led to record flooding in the Mid-Atlantic Region.  In June 2006, D.C. saw 10.43” of rain in just three days (June 25 – 27).  While not the result of a tropical system, there was a large feed of tropical moisture that contributed to make June 2006 D.C.’s wettest on record.

The average monthly June temperature (combining daily high and low temperatures) is 75.2°.  Temperatures have actually been cooler than average on four of the first 10 days this month in Washington, D.C.  Overall, the first third of this month was roughly 1° warmer than average.  D.C.’s average high/low temperatures range from 80°/62° on June 1 to 83°/65° on June 10.  The cooler than average days were partially a function of rainy conditions, but not entirely.  Aside from a high temperature of 90° on June 1, there haven’t been any hot days so far this month.

While NOAA expects the rest of June to be warmer than average in the D.C. Metro Area, there aren’t any heat waves on the horizon over the next one to two weeks.  A “heat wave” is defined as a minimum of three consecutive days with high temperatures of at least 90°.  June is also expected to finish with above average precipitation in Washington, D.C.  That’s partially a function of how much rain has already occurred this month, 2.76” as of June 9 or nearly 75 % of the June’s monthly average (3.78”).