Weathering DC’s Heat Waves !

There has been no shortage of lengthy heat waves in the Nation’s Capital.  Although a “heat wave” is defined as a minimum of three consecutive days of 90°/+ heat, there have been a number of heat waves that have spanned 10 or more days.  Today will be DC’s twelfth consecutive day of 90° heat, making the current heat wave not only the first of 2020, but equal to the longest heat wave Washingtonians experienced last year. 

The current heat wave began on June 26 and will continue for the remainder of the week.  By comparison, DC’s longest heat wave of 2019 spanned 12 days from July 11 – 22.  As the WUSA9 Weather Team predicts, there is an outside chance the Nation’s Capital could have highs of at least 90° every day through the upcoming weekend.  If DC’s heat wave extends to next Monday, July 13, then it will reach 18 days in length.  That would tie DC’s longest heat wave of the last 25 years.  DC residents experienced a stretch of blistering heat from July 22 to August 8, 1999.

What makes the current heat wave different from so many others is the absence of 100° heat.  That 18-day stretch in 1999 produced one day of triple-digit heat.  DC’s second longest heat wave over the last 20+ years occurred during the 2011 summer.  Spanning 16 days from July 18 through August 2, Washingtonians experienced four days of 100°.  July 2011 set a new record for DC’s hottest July and that heat wave played a central role.

Perhaps DC’s most infamous heat wave of the last 20 years occurred during the summer of 2012.  Washingtonians experienced an 11-day heat wave from June 27 – July 8, 2012, when high temperatures reach 100° on five days.  Included in that stretch was June 29, 2012, when the high in Washington, D.C. reached 104° and set a record for DC’s hottest overall June temperature.  That evening was DC’s infamous “derecho,” which caused over a million power outages, many of which lasted up to a week.  The lack of air conditioning for millions of people in the DC Metro Area created a great deal of hardship.  The Nation’s Capital had four consecutive days of 100° heat from July 5 – 8, 2012. 

Irrespective of how long the current heat waves lasts in the Nation’s Capital, it will bear more in common to last year’s heat wave than others since no triple-digit heat is expected.  Prior to last year, the previous time DC residents experienced a heat wave of 10 days or more during July without any triple-digit heat was an 11-day stretch in 1994.