The tremendous thunderstorm with gale force winds that erupted on the afternoon of September 1, 1862, during the Battle of Ox Hill (Chantilly) was the most violent weather recorded on a battlefield during the Civil War. The storm was so unusual in its strength and ferocity that it ranks with the deaths of Generals Kearny and Stevens as the most remembered aspect of the battle.
The following excerpt is from the book Washington Weather by Kevin Ambrose, Dan Henry, and Andy Weiss:
"The thunderstorms that occurred during the [Ox Hill] battle were associated with a strong early-season cold front. The front was also accompanied by strong winds. Before the battle, the wind was strong from the south, recorded by the Naval Observatory in Washington to be at Force 6. The next day, on September 2nd, the Observatory recorded winds from the northwest at Force 4, and military records noted that northwest gales hampered shipping on the Potomac River. The Naval Observatory also recorded that 1.08 inches of rain fell [in Washington] during the storm of September 1st, and included the following remark: ‘Commenced an exceedingly heavy rain, with lightning and thunder, at 5:45 p.m.’ (Robert Ross Smith puts the time at 5:00 p.m. at Ox Hill)."
Here are some additional descriptions recorded in contemporary and historical accounts:
“The advance of Jackson’s column encountered the enemy at Ox Hill, near Germantown, about 5 p.m. … A cold and drenching rain-storm drove in the faces of our troops as they advanced and gallantly engaged the enemy.” General Robert E. Lee, C.S.A., Commanding Army of Northern Virginia
“The fight took place during a terrific storm of rain, thunder and lightning and the enemy at one time drove us back. Night put an end to the contest and we kept the field…It was very cold and we suffered a good deal; we also got very wet.” Jedediah Hotchkiss, Gen. Thomas J. “Stonewall” Jackson’s Topographer
“A beating shower of rain poured upon us during the engagement and for a good portion of the night, blinding and drenching those actually engaged, and almost drowning the line in reserve, who lay on the ground for protection from bullets.” Lt. James Caldwell, 1st South Carolina Volunteers
“During the afternoon a violent thunder storm set in, and a perfect hurricane blow at sunset; but the press of work was such that under the deluge of rain the work of amputation was continued in the open air…” Surgeons on the Second Manassas battlefield reported in New York Herald, September 7, 1862
“It was a beastly, comfortless conflict. Dark clouds rode overhead, like squadrons of horse, shook their black manes, and discharged their angry volleys upon quarreling mortals. The lightning interchanged continuous flashes with those of musketry in the gloomy woods; guns and ammunition became wet and useless. Peals of thunder, roar of artillery, rattle of musketry---night came down on the scene, made it more infernal for a while, and then put an end to the diabolical battle.” Lt. Henry Kyd Douglas, AAAIG to Stonewall Jackson
“A sudden and severe thunderstorm now burst over the field, and the rain fell in torrents; the heavens grew dark, the thunder rolled, and vivid flashes of lightning illuminated the woods. The din caused by our batteries and musketry, and Heaven’s artillery, with the heavily falling rain, combined to render the scene not only impressive, but awful.” William B. Todd, Company B, 79th New York
“A thunder storm of remarkable force occurred at the same time. This war of man and the elements constituted one of the grandest and most terrible scenes which often occurs, while an unseasonable and preternatural darkness settled down over everything, and one could only see such scattered, stunted pines about him as stood within pistol shot, bending and swaying to the fury of the storm except when lurid lightning showed the thick clumps of men packed about the roots of these stunted trees for such slight protection as their branches afforded them from the torrents of rain which swept down on this pine barren country in sheets. Shells were constantly screeching and bullets hissing just over our heads, and the thunder of artillery and of the heavens was, for a long time, entirely continuous, without an instants intermission.” Capt. Edwin Marvin, Company F, 5th Connecticut
“What a grand spectacle the Chantilly fight presented! A terrible rainstorm with terrific thunder and lightning prevailed during its continuance---this combined with the booming of cannon and the rattle of musketry, made up a most indescribable scene, outrivaling pandemonium itself. It was a terrific, horrible, phantasmagoria.” Major Oliver Bosbyshell, 48th Pennsylvania
“The roll of musketry and the roar of cannon left all of us unmoved, but the crash of thunder and the vividness of the lightning, whose blinding flashes seemed to be in our very midst, caused the uneasiness and disturbance among some of the bravest of men.” Private Andrew Greely, 19th Massachusetts
“Just as they got into position a terrific rain-storm burst upon them; the rain poured down in torrents, and heavy peals of thunder and brilliant flashes of lightning, mingled with the storm of battle was terrible in the extreme. It seemed as though the artillery of heaven was vying with that of man, and indeed the roar of the battle was almost lost in that of the storm, making applicable Shakespeare’s lines: ‘Have I not heard great ordnance in the field / And heaven’s artillery thunder in the skies.’” Kate Scott, History of the 105th Pennsylvania