How hot does it usually get in Washington, D.C. during the summer?

(Ian Livingston)

(Ian Livingston)

Day time highs soared into the mid-and-upper 90s across the region last week, and temperatures did not fall below 80 for a record-setting 138 hours. But, generally, the extreme heat has been somewhat less frequent and intense than horrifyingly summers of 2010-2012. Let’s hope it stays that way.

So what’s typical for extreme heat in the D.C. area?

Compared to winter lows, the hottest readings fall into a fairly narrow range. We live in a relatively consistently hot and muggy place during summer.

Just how hot should we “expect” the most extreme summer high to be? How about the toastiest low?

(Ian Livingston)

(Ian Livingston)

Using the current 1981-2010 climatological normal period, the average highest temperature of the year is a scorching (rounded, as are all that follow) 99 degrees. When it comes to the warmest low, it’s a sweaty 79.

If for some unfortunate reason the last three years of record heat were our new normal, we might expect to see a high of 104 and a low of 82. No thanks.

The highest temperatures of the summer year-to-year have been what I would consider remarkably consistent since the late 1800s when records began. There is of course fluctuation, but the bounds have remained remain more or less the same.

(Ian Livingston)

(Ian Livingston)

The highest high is the 106 that occurred on August 6, 1918 and July 20, 1930. The lowest annual high was a chilly 92. This happened as recently as 2004, and as long ago as 1886.

The highest low temperatures annually, while confined to a very narrow range from 73 to 84 throughout history, do appear to be making more of an upward move as we progress. Undoubtedly some of this is related to the urban heat island that is growing across the area.

As an example, those summertime lows of 80 degrees we’ve been sweating through recently have shown up as long as the record as been around. However, they are now showing up with considerably more frequency both year-to-year and in times per year.

Max highs and lows of the 2000s….

2000: 94, 75
2001: 97, 79
2002: 100, 80
2003: 94, 76
2004: 92, 76
2005: 97, 78
2006: 101, 81
2007: 102, 80
2008: 98, 78
2009: 97, 76
2010: 102, 81
2011: 104, 84
2012: 105, 82
2013*: 97, 81

* so far

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