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Posted at 12:47 PM ET, 07/05/2012

Worst heat wave ever? Washington, D.C. ties record for most straight 95+ days, more coming


Asterisk indicates daily and monthly record high temperature. Gray text indicates predicted temperature.
In terms of the duration of a punishing heat wave, the current spell has arrived at historic levels in Washington, D.C..

For the 8th straight day (as of noon today, when it was 97), the temperature has reached at least 95 degrees - tying 2002, 1993, and 1987 for the most such days on record.

Related link: 90 degree days in Washington, D.C.: Yearly, seasonal and monthly averages and extremes

It’s very likely we will add three more days to this tally through Sunday - making this heat wave in D.C. history unmatched with respect to the miserable combination of length and intensity.

How hot might it get?

Triple-digit heat is possible daily through Sunday. The hottest day is likely to be Saturday, when highs may reach 102-106.

What are the records? Will they be broken?


NAM model projects 5 p.m. temperatures at or above 105 degrees Saturday. (Storm VistaWxmodels.com)
* Today’s record high is 102. With a 97-degree reading as of noon, a tie of this record is achievable.

* Friday’s record high is 103. This one may be tough to get.

* Saturday’s record high is 102. We have a decent chance at this one and there’s a very outside chance we could flirt with our all-time high temperature (any date) of 106 set in 1930 and 1918.

* Sunday’s record is 100 - and while clouds may cool us down a bit relative to Saturday, we could make a run at this.

What about the humidity?


NOAA’s Hydrometeorological Prediction Center predicts heat indices of near 110 Saturday near Washington, D.C. (NOAA)
Humidity levels are going to remain moderate to high, adding 3-8 degrees to what the air temperature actually feels like - the heat index. Maxium heat indices through Sunday will be in the range of 100-107, except possibly near 107-112 on Saturday.

What’s driving the heat?

The cause of the heat wave is a HUGE area of upper level high pressure - i.e. a heat dome - that has set all sorts of monthly and all-time records from the Rockies to the Southeast U.S. in the last one to two weeks. Wunderground’s Jeff Masters called the heat wave “one of the greatest in recorded history.”

The heat wave has been amplified by drought - drying out soil moisture over large parts of the country. As of today, the U.S. Drought Monitor shows 56 percent of the country in drought - the largest area in its 12-year record.


As of this morning, 56 percent of country was covered in drought and at least 76 percent abnormally dry. (U.S. Drought Monitor)

Environmental factors intensifying the heat?

A combination of the urban heat island effect (an increase in heat absorbing surfaces like asphalt and concrete) and climate warming from increasing greenhouse gases have also almost certainly intensified the heat to some degree - making records more likely now than in early decades.

When does it end?

A cold front pushing through the region late Sunday into early Monday will bring a return to more normal mid-July temperatures early next week, with highs in the upper 80s and low humidity.

Capital Weather Gang’s Ian Livingston contributed to this post.

By  |  12:47 PM ET, 07/05/2012

Categories:  Latest, Extreme Heat, Droughts, Local Climate

 
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