May 2011 closes out the meteorological springtime, and it ended on a very hot pre-summer note. The scorching 98F degree reading on May 31st was only one degree shy of the hottest temperature on record for the month (99F in 1991). We exceeded 90 degrees three times in May, which is about twice the normal (1.6 times). Our coldest reading of this month was a triplet of crisp, 46 degree lows back on May 4-6 (wow, that seems so long ago!).
Overall, it was warmer and drier-than-normal for Washington, D.C. The precipitation story is probably a bigger concern with only about 1/3 of normal falling this past month. We could use a bit more rain here in June as I’m sure most of you have noticed recently.
The main driver of our warm and dry May was a jet stream pattern that sent cool troughing into western North America. The jet stream route was more focus toward the Midwest and north of us (this pattern delivered lots of rain to the eastern Midwest, but not-so-much here).
Looking at the master chart of all D.C. May temperature averages all the way back to 1871, we find that 2011 was in the top-tier of years, but still about one degree cooler than May 2010. Our average of 68.3 was still almost five degrees cooler than the hottest May on record, set in 1991 but 9 degrees above our coldest Mays on record from 1881 and 1907.
The National Weather Service publishes nice monthly assessments usually within a week of the close of each month.
You can click on your closest airport location here:
Historical Washington, DC data provided by NOAA and Speedwell Weather .