For 134 straight hours (7 a.m. on July 23 to 9 p.m. on July 28), the temperature never fell below 80 degrees, the second longest such streak on record.
With an average temperature of 82.7 degrees, the month finished 2.9 degrees above normal, an anomaly only surpassed since 2000 by the trio of super hot Julys spanning 2010-2012.
The high temperature reached at least 90 degrees on 23 of 31 days, ranking fourth most on record (tied with July 1988):
Rains were quite sporadic last month, with some areas drier and some areas much wetter than the official reporting stations. D.C. posted a total rainfall of 3.13 inches, which is below the normal of 3.73 inches.
Many areas reported more rainfall including Baltimore that logged over 6 inches while Dulles was closer to D.C. with just over 3 inches.
D.C.’s 3.13 inches was the sixth driest of the 2000s, embedded toward the middle of the overall historical range dating back to 1872 — not too dry or too wet.
Here is the list of July 2016’s extremes:
Our biggest day for records was July 25, when D.C. had its first 100-degree reading in four years, tying the record set in 1930. Baltimore also hit 100, tying the record set in 2010. Dulles Airport, which joined the 100-degree club, topped its prior record of 98 from 2010.
Very warm low temperatures were perhaps more notable than the highs. D.C. tied or broke warm minimum records three mornings in a row (July 25-27), as the mercury bottomed out in the very muggy 80-81 degree range. Dulles set record high minimums on July 26-27 as well as on July 13.
Dulles set one other interesting record during the month: Its cool high of 72 degrees on July 4 was only 2 degrees warmer than last Christmas Day (2015) and low enough, by a degree, to break 1979’s record for coolest high temperature.
The United States was hotter than normal from coast-to-coast as a developing La Niña started evolving in the Pacific Ocean. Such a pattern usually leads to large-scale ridging patterns over much of the country, sometimes referred to as “heat domes,” as we’ve seen this summer so far. The jet stream ran along the northern tier of the United States and into southern Canada.
The estimated surface temperature differences from normal during July show the widespread coverage of above normal temperatures:
January to July 2016: Warm and dry so far
The slightly drier than normal conditions in July result has shifted 2016 to the sixth driest position of the 2000s. There is a fairly big drop between 2016 and the fifth driest — 2010 — as shown on the chart below. But we don’t expect August to be dry enough to drop us much lower than this (if anything, we may gain some ground back).
July’s temperatures were hot enough to shift 2016’s ranking one position warmer to seventh warmest of the 2000s. The combination of a milder-than-normal winter and hotter-than-normal summer are keeping temperatures squarely toward the warmer side of normal.
I’m not sure when we’ll have our next cooler than normal month, but we’ll have a better chance at that in the final quarter of this year as a weak La Niña, should it develop, gently favors chillier cold season temperatures.
For further information
The National Weather Service publishes nice monthly assessments about five days into the start of the next month. You can click on your closest airport location here:
Jason Samenow and Ian Livingston contributed to this post.