DC issues extreme heat warning as indexes top 110

The heat in Washington, which was at full tilt in mid-June, is becoming unbearable.

Tuesday marked the fifth straight day with temperatures of at least 97 degrees and the 22nd day with temperatures of 90 degrees or higher this year. Heat indexes, which factor in oppressive humidity, rose to around 110 — higher than nearly anywhere else in the United States. The harsh conditions prompted the National Weather Service to upgrade D.C.’s heat advisory to an extreme heat warning.

Temperatures are expected to rise above 35 degrees Celsius again on Wednesday and heat warnings are in effect for the third day in a row.

The nights have been sultry in the meantime. We have reported lows of 80 degrees or higher several times this summer after a break of five years. Before the year 2000, such warm nights were exceptionally rare.

The warm days and humid nights make for the second warmest start to summer on record.

While there may be a break in the heat on Friday, it won’t last long. The warm weather pattern is likely to resume over the weekend and intensify next week.

According to the Climate Shift Index from Climate Central, a science communications agency, the risk of human-caused climate change has doubled in the Washington, DC region.

The second warmest summer ever recorded

Using the meteorological definition, summer began on June 1. The current average temperature of 80.5 degrees since then is only behind 2010’s 80.8 degrees among the warmest years to date. Rounding out the top five are 1994 (80.1), 2011 (79.4) and 2012 (78.9).

As of January 1, this is also the second warmest year on record with an average temperature of 58.7 degrees, trailing only 2012’s 59.3 degrees (which was the warmest year on record). The United States also has the second warmest year on record.

Since we turned on the heating in mid-June, abnormally hot afternoon temperatures have been the norm. The average since June 1 of 90 degrees is the third highest ever measured, after 2010 (90.4) and 1994 (90.6).

The 22 days with maximums of at least 90 degrees is eight days earlier than normal so far. Normally we have not seen so many days of 90 degrees until the end of July. Last year we had only 10 such days up to that date.

In addition to all the 32 degree Celsius days, we have had nine with a maximum temperature of at least 36 degrees Celsius, including the first day of 38 degrees Celsius since 2016. So far, the count is only behind 1991, when there were nine, and 2012 with 12.

We’ve now had five days in a row of temperatures of at least 97, and on Wednesday the streak will likely last six days, tying the second-longest streak ever after the seven in 1953.

Low temperatures so far this summer are the second warmest on record. The average low of 71 degrees is only slightly cooler than the 71.2 degrees recorded in 2010 — which had the warmest nights yet.

We have already recorded four nights with lows of 80 degrees or higher, three of which were between Saturday and Monday. We will likely add another Wednesday, bringing the total to five. The most lows of 80 or higher ever recorded in a year is seven, last measured in 2016.

The current heat wave, which began on July 4, is expected to end on Friday. That’s when clouds and some tropical moisture, pushed northward by the remnants of Hurricane Beryl, will briefly take over the region, bringing temperatures down a bit (but not the humidity). A chance of rain — much needed as the drought intensifies — should keep highs in the low 90s, though the forecast could still be drier and warmer.

In addition, highs of 90 or higher are likely to return in the coming two weeks. With average highs of 90 through July 27, warm weather is expected. But computer models predict that temperatures have a good chance of rising above the norm, well into the 90s and sometimes almost 100.

Jason Samenow contributed to this report.

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