Welcome Summer

Summer officially arrives in North America on the summer solstice which is this Saturday, June 20.  That’s also DC’s longest day of the year with the most hours of sunlight.  The first half of the month has been unremarkable weather-wise compared to past June’s.  Although temperatures have been 2.5° above average through June 15, no record challenging high temperatures have occurred.  In fact, there have been more days with high temperatures in the 70s (four) so far this month than there have been days in the 90s (three).

June weather isn’t a reliable indicator of what the rest of the summer will be like.  For example, June 2016 had only five days in the 90s with an average monthly temperature within a degree of average.  However, July, August and September 2016 were each at least 2.9° warmer than average.  July through September 2016 was one of DC’s hottest three-month periods on record with 53 days of 90°/+ heat, including four days of triple-digit heat.  

Although June 2016 was a drier than average month in the DC Metro Area, there were several days of severe weather including on June 8 and June 16.  The dominant weather story the rest of that summer was the intense heat, as well as the historic flooding in Ellicott City, Maryland that occurred on July 30, 2016.  

The last time June was cooler than average in the Nation’s Capital was in 2009.  That was an interesting month that had the same number of days with high temperatures in the 60s (two) as in the 90s (two).  Measurable rainfall occurred on 11 days, including two days with at least an inch of rain, which produced a month with a rainfall surplus of more than 2”.  In an unusual turn of events, July 2009 was more than 2° cooler than average, while August 2009 was nearly 2° warmer than average making it the warmest month of the summer.

As cool and wet as June 2009 was, the two subsequent June’s ranked among DC’s four warmest on record, with each featuring triple-digit heat.  No triple-digit June heat has occurred in the Nation’s Capital since 2012.  

Dating back to the early 1990s, the Nation’s Capital has averaged triple-digit June heat roughly once every five years.  However, temperatures won’t even reach the 90° plateau again before this weekend.  If June 2016 was any indication, residents of the DC Metro Area should enjoy these comfortable May-like highs in the 70s while they last.  That’s because the hottest weather of the summer doesn’t typically arrive until July and August.