Putting the Heat in Perspective

Forecast for Washington, D.C.  (Source: WUSA9)

Although the most significant heat wave in several years began yesterday when the high temperature reached 90 degrees in the Nation’s Capital, the dangerous heat will arrive today.  It’s already been a dangerously hot week across much of the country with heat advisories in effect today from South Dakota to Louisiana to Ohio.  While heat advisories and excessive heat warnings are often issued on a localized basis during the summer months, the extent to which they’re currently in effect is unusual.  Here is a good National Weather Service link that explains the different criteria for heat advisories.

Triple digit heat is relatively rare in the DC Metro Region.  While there have been a total of 32 days at or above 100 degrees in Washington, D.C. (measured at National Airport) since 1993, there have been only seven instances of two or more consecutive days at or above 100 degrees.  Six of those streaks have occurred in July, with the longest being a four day stretch from July 5 – 8, 2012.  The summer of 2010 was the first summer in the Nation’s Capital to feature five or more days at or above the century mark since 1997.

Given the potentially historic heat on tap for the next few days across the eastern United States, it’s a good time to review some of the historical heat waves in Washington, D.C.  During the last 25 years, triple-digit heat has occurred in the Nation’s Capital roughly every three to five years.  Since 1993, there have been consecutive days of triple-digit heat five times in July.  Triple-digit heat has also occurred during five June’s and August’s in that time.  However, July has had the highest total number of days (20) at or above 100 degrees.

The hottest temperature on record is 106 degrees in Washington, D.C., which occurred twice – both times were before National Airport opened in 1941.  The hottest temperature on record at National Airport is 105 degrees which occurred on July 7, 2012 and August 17, 1997.  The hottest temperature on record at Dulles Airport in Sterling, Virginia is 105 degrees on July 22, 2011.  Meanwhile, Baltimore’s hottest temperature on record is 107 degrees on July 10, 1936.

Although not typical in this part of the country, the thermometer will approach 100 degrees during the next few days.  Even if there isn’t any triple-digit heat the next few days, high temperatures are poised to be in the 90s for the balance of next week.  My colleagues and I on the WUSA9 weather team will keep you apprised of the latest weather forecasts – and if any record highs are set.