June: How Does 2021 Compare?

 

This is the first June since NOAA updated its climate data to reflect the 30-year period from 1991-2020.  As a result, average high and low temperatures, as well as average monthly temperatures in the Nation’s Capital are considerably higher than they were previously.  That’s because the decade of the 2010s was much warmer than the 1980s across most of the United States.

While average temperatures during the first three weeks of June were more than one degree above average, many Washingtonians wouldn’t view this as a particularly hot June.  In fact, by most standards this month has been relatively comfortable.  For four consecutive days last week (June 15 – June 18), temperatures were not only cooler than average but dewpoint temperatures on two of those days remained in the upper 40s to around 50° creating stellar, almost fall-like weather.

While conditions in the few days since then have been noticeably warmer and more humid, there have still only been four 90° days in the Nation’s Capital so far this month.  Washington, D.C. has averaged between seven and eight 90° June days over the last 30 years.  Last June finished with nine 90° days in the Nation’s Capital. 

DC’s highest total of 90° June days was the 18 that occurred in June 2010, which finished as DC’s warmest on record.  By comparison, only two 90° days occurred in Washington, D.C. in June 2009.  There are a few more 90° days in the seven-day forecast my colleagues and I on the WUSA9 Weather Team are working on, so the total of 90° days for June 2021 should rise. 

Whether or not June is a very warm month is not a good indicator of what the rest of the summer will be like, however.  For example, June 2016 finished with only five 90° days, but the 2016 summer went on to become one of the hottest on record in the Nation’s Capital.

This month has already become DC’s wettest since last November with 5” of rain as of June 21.  The majority of that rainfall occurred on three days when a combined total of 4.62” fell.  There are a few more rain chances in the Nation’s Capital so the monthly rainfall surplus should continue to grow.  That’s good news since April and May were each drier than average in Washington, D.C.