From the ABC 7 Weather team

Washington, D.C. heat this week by the numbers

May 29, 2013 - 09:48 AM
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Well above average temperatures are here, but are we talking record breaking heat?

After a cool and comfortable spring, it's back to reality as a stretch of 90 degree heat is upon us. Reagan National Airport (DCA) already hit 90° once back in April, but we haven't had long stretch of heat since last summer (late July/early Aug.) when there were 10 consecutive 90° days. Well, say hello to our first heat wave of 2013. It'll only last through Saturday, but you'll still notice it.

The average high temperature, record highs and going forecast are shown below. Clearly our temperatures are well above average but likely not within reach of records. As a rule of thumb this time of year, the mercury needs to climb into the upper 90s to tie or break a record at DCA.



Temperature Comparison

Lastly, the term "heat wave" has a very loose definition and is quite subjective. Here is how it is defined in the Glossary of Meteorology by the American Meteorological Society:

"(Also called hot wave, warm wave.) A period of abnormally and uncomfortably hot and usually humid weather."

and

"To be a heat wave such a period should last at least one day, but conventionally it lasts from several days to several weeks. In 1900, A. T. Burrows more rigidly defined a "hot wave" as a spell of three or more days on each of which the maximum shade temperature reaches or exceeds 90°F. More realistically, the comfort criteria for any one region are dependent upon the normal conditions of that region. In the eastern United States, heat waves generally build up with southerly winds on the western flank of an anticyclone centered over the southeastern states, the air being warmed by passage over a land surface heated by the sun. See also hot wind."

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