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Posted at 12:24 PM ET, 03/21/2012

From March heat in Washington, D.C. to a summer scorcher?


Cherry blossoms in Washington, D.C. enter into peak bloom on Sunday, March 18, 2012, about two weeks earlier than usual. Photo (a stitched panorama of 8 vertical images) by author.
A few weeks ago, we examined whether our abnormally warm winter would be followed by a hot sumer. We found historically warmer than normal winters were followed by cooler than normal summers slightly more than half of the time, but there was no meaningful correlation. Nothing to worry about, then, if your A/C is on the fritz, right?

Then came this March. So far, the average temperature is running an incredible 11.0 degrees above normal. With no massive cool downs in sight, odds are good that we can match or top the previous warmest March on record in 1945. That month had an average temperature of 56.2 degrees, or 9.4 degrees above the current March normal of 46.8 degrees. So is a warm March a harbinger of a hot summer?


The 20 top wamest March temperatures and the summer (June-August) temperatures that followed. The red line is the current summer normal temperature. The blue line is the current March normal.
Examining the top 20 warmest Marches, the “signal” favors a cool summer. Only four of the 20 warmest Marches were followed by a warmer than normal summer (average temperature of 77.7 degrees). 15 were below normal, and one was exactly normal.

1945, the warmest March on record at this point, had a summer average temperature 2.5 degrees below the current normal. Of the top 5 warmest years in March (1945, 1921, 1946, 1977 and 2000), only 1977 had a warmer than normal summer and barely so, averaging 78 degrees.

The average of the top 5 warmest Marches when rolled over to summer comes out to 75.2 degrees. That’s cooler than every June-August dating back to 2000. In 2000, the average summer temperature was nearly 3 degrees below normal, and had only 12 days (a third of the current average ) above 90 degrees! But alas, preceding that “cool” summer was the 5th warmest March on record....

Finally, we can also examine the 18 years on record during which *both* meteorological winter and March was warmer than normal and look at what kind of summer followed.


Summer temperature departures for 18 years which had a warmer than normal meteorological winter (Dec-Feb) and then also a warmer than normal March. From 1872, 12 were cooler than the current normal of 77.7 degrees and eight were warmer.

Ten of the 18 years when temperatures were above normal during both of these periods featured cooler than average summer temperatures. The other eight had above normal temperatures. The warmest summers of the group were 1.7 degrees above normal and the coldest were 2.9 degrees below normal.

But during the current climate period from 1981-2010, the combination of a warmer than normal winter and warmer than normal March was followed by a warmer than normal summer about 64 percent of the time.

Despite the long-term data, in light of recent trends, if I were betting, I’d predict a warmer than normal summer. But, the Capital Weather Gang summer outlook is still ahead with plenty of time for change. What do you think?

Related links:

Warmest astronomical winter on record in Washington, D.C.

Third warmest meteorological winter on record in Washington, D.C.

By  |  12:24 PM ET, 03/21/2012

 
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