On July 21, 1861 - 150 years ago - the first major battle was fought between poorly trained Union and Confederate troops about three months after the Civil War began. The battle, an early victory for the Confederacy, was said to have been waged during a “hot and sultry” period. It was said to be so hot that, by the time hostilities began, bodies of slain troops at the earlier (July 18) battle site of Blackburn’s Ford were bloated and “unrecognizable.”

But just how hot was it during that fateful period and how did the weather compare to the heat wave now enveloping Washington, D.C. (and much of the country)? Aside from anecdotal comments derived from diaries and letters, etc., a clearer picture, is available from the noted weather observer Rev. C. B. Mackee.**

Despite the various battlefield reports of oppressive heat and humidity, Mackee’s records, with a few exceptions, reveal otherwise. It appears that the weather before, during, and after the Battle of First Manassas was no match for our current heat wave: although Mackee’s 2:00 p.m. D.C reading on July 20th was 90 degrees, the next day—the day of the battle—the 2:00 p.m. reading was only 80.* Thereafter, the temperature didn’t reach 90 again until July 30th.

As noted in the Capital Weather Gang’s posts on March 8, 2011, “The Weather Leading up to the Civil War” and April 11, 2011, “April 1861: The War Between the States begins— what was the weather like?”, Mackee was a diligent amateur meteorologist. He rarely missed his scheduled observations, which were made at 7:00 A.M., 2:00 p.m. and 9:00 p.m. Even when his thermometer broke, he was able to obtain substitute readings from a family member in Richmond, which was better than nothing at all, he reasoned.

Admittedly, Mackee’s records didn’t include humidity or dewpoint readings, which, if high, could have raised the discomfort level considerably. Nevertheless, with only eight 90-degree days, eighteen 80-degree days, and even five 70-degree days during the month of July, 1861, today we might call that a “pleasant” month, even though it rained on many days. On one of those rainy days--July 22nd, the day after the battle--temperatures barely hit 70 during a 1.5 inch downpour. (Richmond recorded 8.25 inches of rain for the month.)

What does this comparison of July 1861 weather with July 2011 weather teach us, if anything, about the weather we might expect in the year 2161, 150 years from now? My crystal ball isn’t quite that big but hopefully, our descendants won’t be referring to the weather of July 2011 as “a piece of cake.”

* Post script: Perhaps it was because July 21 dawned “bright and beautiful, under a strikingly blue sky,” that one of the more bizarre occurrences of the entire Civil War took place, when “well-dressed socialites and spectators, armed with refreshments, went out to Manassas to watch the battle.” Eventually, however, reason prevailed and the crowd shared all they had with the defeated Union soldiers, as they all retreated back to Washington-- A Narrative of the Battles of Bull Run and Manassas Junction, July 18th and 21st, 1861 (Charleston, S.C.: Steam-Power Presses of Evans & Cogswell, 1861), 10.

**According to Robert K. Krick, author of Civil War Weather in Virginia, Mackee maintained what is believed to be the only continuous record of D.C. weather conditions for the months immediately preceding the Civil War until its completion.

Related: Comprehensive Civil War 150 coverage

CWG’s Kevin Ambrose contributed to this post.