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Surgeons kept temperature, pressure, wind speed, and humidity records—but they didn’t know what to do with the data

Predicting weather has always been a military priority in warfare. From consulting oracles and shamans to the evolution of modern meteorological techniques that dictated much of the course of World War II (D-Day Allied success, German winter failure in Russia, etc.), campaigns have fallen to ruin or encountered spectacular success, depending on the whims of nature. The Civil War was arguably the first “modern” war and provides a perfect case in point of the ongoing struggles to master information about the weather for military purposes.

By the Civil War, the major technologies available to quantify and study weather included mercury thermometers to measure temperature (Daniel Fahrenheit, 1714); barometers to measure atmospheric pressure (Evangelista Torricelli, 1643); the telegraph, which allowed coordination of bigger data pools across wider areas (Samuel Morse, c. 1830s); anemometers to measure wind speed (John Thomas Romney Robinson, 1846); hygrometers to measure humidity (Nicolas Cusa, c. 1450s); and hot air balloons (de Rozier and d’Arlandes, 1783), which increased the geographical scope of visual observation and data collection. These advancements in turn led to the first pooling of aggregate weather data, crude predictive analysis, a growing network of volunteer and military weather observation stations, and the creation of crude weather maps. Due to a lack of resources and focused interest, the U.S. Army lagged behind some civilian efforts in some areas of weather study.

A Union fleet was caught by a Nor’easter in January 1862 as it tried to cross the bar at Cape Hatteras on the way to attack Roanoke Island. Several ships were lost. (Print Collector/Getty Images)

The Army did institute weather-reporting protocols early. According to the National Archives’ records of the Weather Bureau, army surgeons at various levels of rank were directed in 1814 during the War of 1812 with Britain to collect local weather data and record it in logs or diaries, ultimately to be reported back to the Surgeon General. According to the U.S. Army Medical Department, this was “systematized by 1818 to include changes in temperature, barometric pressure, precipitation, wind direction, and severe weather events.” The data was compiled in aggregate in 1826, 1840, 1851, and 1855. The Navy also had weather procedures. 

The U.S. Army Medical Bureau’s regulations for surgeons includes a page for recording weather observations. (National Archives)

Many of these records are available on microfilm. The intention was not to make physicians into weather reporters or meteorologists, but rather to acknowledge and study the connection between climactic conditions and army health, and doctors were the logical point of contact for collecting and using that information. They were not necessarily in the predicting business, but rather in the correlating business.

This procedure continued up to and through 1861, although there was some variation in the thoroughness with which officers approached the task. Colonel Albert Myer, for example, while serving as a medical officer in Texas before the Civil War was also assigned the duty of reporting local weather conditions and creating such records and he did so fairly routinely. Other officers were not as diligent. This pairing of medicine with science made sense at the time, since climate and weather could both impact the health of the army, and many doctors did have some basic scientific training. Still, it did not represent a meteorological science in the way the 20th-century armies would recognize it as its own specific specialty, or even recognize the more strategic military necessity for it which would become increasingly clear as the American Civil War progressed.

A review of U.S. Army regulations in 1861 finds mentions of weather in only a few places but records do include the requisite forms the medical officers were to use to report weather. Almost all the textual references in the regulations themselves relate to protecting equipment, camp routines, and fortifications from bad weather, rather than guidelines for predicting weather or reporting such information for purposes of strategy or tactics. It was mentioned that adverse weather could provide cover for surprise operations, which is the genesis of several famous Civil War incidents. Nevertheless, it remained primarily the medical department’s responsibility to simply report on weather conditions, and then forward them to the Surgeon General using the requisite forms, even though the civilian science of weather and weather prediction was quickly advancing beyond the expertise of army doctors and surgeons, as well as the army’s growing need for prediction and forecasting by the time of the Civil War.

The Confederate Army based its regulations largely on those of the pre-war U.S. Army. Even so, no overt reference to weather is made in their forms or in the 1862 Regulations of the Medical Department of the Confederate States Army. Instead, there is only a vague reference in the directions for completing medical form No. 1:

[Form No. 1] will be accompanied with a general Sanitary Report, to be written on alternate pages of foolscap paper, with a margin of one inch on the left side of each page, and to be folded in four equal folds; in which the medical officer will furnish information…such as the medical topography of the station; the climate; prevalent diseases in the vicinity…

In the CSA general army regulations, most of the nearly two dozen references to weather are mainly related to the practicalities of constructing fortifications, care of weapons, and dispensing with ceremony when conditions were bad. A few references, such as item No. 659, do address weather tactically:

Stormy weather, fogs, extreme heat, and the night above all, are favorable to the success of ambuscades; when the enemy are careless, the break of day is the best time.

The regulations for troops on water-borne transports also hints at the tactical necessity of predicting weather: 

The bedding will be replaced in the berths at sunset, or at an earlier hour when there is a prospect of bad weather; and at tattoo every man not on duty will be in his berth.

Some physicians did practice their own informal methods of weather forecasting. John Ebersole, surgeon for the 19th Indiana Volunteers, often lapsed into meteorological jargon and prediction in his journal, with entries mentioning that today would likely be “clear with scattering clouds,” or, “marched 15 mortal hours in a drenching rain in mud and slush.” “Today continued the rain and wind from the north east cool and disagreeable—hard on the soldier.” He clearly made the connections to army wellness, sometimes in ways that were counterintuitive. “I hope the hard shower was conduce [sic] to the health.”

Other surgeons, mostly from agricultural backgrounds, interpreted the weather through the eyes of farmers: “[a] fine rain today,” and this gentle rain “helped the growth of vegetation.” The enlisted men with a surgeon named Cheuvront who trudged through endless muddy marches may have disagreed with his approval of the “fine” rains that he recorded with great frequency.

Harsh weather (and the lack of accurate prediction) led to both the tragic and the sublime. In January of 1863, for example, an unanticipated Northeaster roared up the coast and turned Union Maj. Gen. Ambrose Burnside’s massive winter invasion of Virginia into an epic muddy disaster (Washington Weather says 3.2 inches fell). Roughly a month later, the same unpredictable weather brought a heavy snowstorm to central Virginia, during which Confederate Lt. Gen. Stonewall Jackson witnessed the war’s largest snowball battle between thousands of CSA troops (North Carolina’s claim to victory is still disputed).

Weather impacted all campaigns but obviously played a more important role in some more so than in others. The Confederate invasion of the New Mexico territory provides a fascinating case study that illustrates the point. Using official records as well as personal accounts such as the diaries of Sergeant A.B. Peticolas, it becomes clear that the weather impacted planning, tactics, and camp life, and that an inability to predict it accurately changed successes into failures, especially when insufficient resources were available to mitigate the effects of weather (wet powder, flooded rivers, ruined food, slowed mobility, sickness, etc.)

Peticolas writes about these matters first-hand, such as in this March 8, 1862, entry:

The wind increased to almost to a hurricane. Clouds of sand came driving against our backs, and the whole atmosphere was dark with the heavy clouds of sand. The pebbles dashed stingingly against our backs, and our eyes were almost put out by the sand. I put my hat up over my face and thus protected my eyes as much as I could. Fortunately for us, the wind was on our backs and served to help us along.

The Confederate invasion of the desert Southwest failed in part because the weather was so harsh and unpredictable. “The weather… claims our exclusive attention,” Peticolas later wrote. The commanding general of the invasion, Brig. Gen. Henry H. Sibley, was often forced to make important campaign decisions in the midst of terrific storms that altered between sand, rain, snow, and sleet. Another soldier said that the snow and sleet came at them so hard that it, “almost pelt [sic] the skin off our faces.”

Weather often caused fighting to become secondary to survival. While chasing Confederate General Robert E. Lee north after his victory at Chancellorsville in 1863, Union soldiers marched through a rainstorm so intense that it seemed worse than battle. “It was with the greatest difficulty that we could distinguish even a faint outline of each other marching side by side; and it was only by continually shouting to our comrades that we were enabled to keep our places in the ranks.”

Sometimes, the weather was noted after the battle, as if the two were correlated. Robert E. Lee’s artillery chief, Colonel E.P. Alexander, noted after the fighting at Chancellorsville ended that “there came on one of the remarkable storms which on many occasions closely followed severe engagements.” It was as if battle on such a massive scale actually changed or caused the weather. “The rainfall was unusually heavy and continued long after dark…It hurried the efforts of the Federals to cross the [Rappahannock] river, as rapidly rising waters overflowed the approaches to their bridges.”

Although medical officers normally recorded the weather, and some no doubt also anticipated it, it was the enlisted men who engaged in constant conversation about what might be coming. Their attempts at weather prediction were not always accurate but represented a type of “forecasting” that we would easily recognize today.

“Weather cloudy and still this evening,” Peticolas wrote, “with strong implications of falling weather.” (One wonders how he would know?)

There can be no doubt that many officers and leaders pondered and tried to anticipate the weather. This was in part why armies didn’t move in the winter, because the weather was unpredictable. But there are tantalizing few references to rational, predictive analyses going on beyond general climatic characteristics which dive into actual daily weather forecasting. Most weather tasks were reactive rather than proactive—Lee’s cavalry monitored the water levels of the Potomac River after the Confederate retreats from both northern invasions to see when it would be safe to cross—but they didn’t consider themselves weather forecasters. They were river-watchers.

The navies on both sides had tremendous incentives to be logging and predicting weather. But surprisingly, the war interrupted that process. According to Phillip Brohan:

In the prewar Navy, Lt. Matthew Maury pioneered the science of meteorology. He went South, however, and his work was interrupted for the course of the war. (Library of Congress)

A key point about the U.S. Civil War is that it put a stop to [Confederate Navy Commander] Matthew Maury’s pioneering collection of marine weather observations. If you look at the number and coverage of the marine observations, we currently have available, you can see a dramatic drop-off in 1861. Because Maury joined the South, coverage didn’t get back to pre-war standards until about 1880.

Some, like Alexander, even suggested that military action could create local weather. He called the vast clouds that were stirred up by marching armies, “army dusts,” and mentioned that he, “acquired more experience” with the intense, dark columns as the war went on. One in particular, was noted by Alexander and another signal officer prior to the First Battle of Manassas as one of the largest they saw during the war.

Historian Allen C. Guelzo in his account of Gettysburg suggests that, “The incessant discharging, blasting, cracking, and pounding created its own miniature weather system, and a soldier in the 16th Mississippi was amazed to see that ‘birds, attempting to fly, tumbled and fell to the ground.’” Like others, soldiers at Gettysburg were amazed by the smoke and dust. “The billows of smoke expelled by the massed thousands of firearms, just by themselves, ‘shut the combatants from sight.’” The local weather could also produce sound anomalies known as acoustic shadows, during which the roar of battle was incessant in one direction, and inaudible a few thousand yards in another direction.

But apart from local conditions—even on the enormous scale of Gettysburg—weather was much more important than the resources and technology allocated to it. It is clear that in addition to fretting about weather, everyone from Lee and Grant to most enlisted men talked about and guessed about the weather. The wonder is that not more resources were ultimately allocated to rational, empirical prediction.

Weather also resulted in direct casualties. Ships could swamp and sink; horses and men were killed by lightning strikes. The winter of 1864-65 was unusually harsh in central Virginia. For the duration of the Siege of Petersburg, Confederates suffered an unusual number of frost-related injuries, cold-related ailments, and desertion due to cold and hunger. Firewood became so scarce that the front lines took on a lunar landscape-like appearance. 

There can be no doubt that weather affected the course of the war, from the worst drought in recent history, to the record-breaking winter of 1864-65 during the Siege of Petersburg. The November 1861 hurricane was a disaster for the navies on both sides.

The science of meteorology would explode immediately after the war. In 1870, Chief Signal Officer Albert J. Myer formally established the weather service for the army. Naval records resumed in full force. The U.S. Weather Bureau was formalized in 1890. But during the war, leaders and officers were often guessing, and seldom checked with medical officers to try and identify recurring patterns, or to generate a more formalized system of forecasting.

By the 20th century, all modern armies and militaries would clearly recognize that weather prediction controlled ultimate success, and that science could bring many weapons to bear in that battle. Today, modern war means modern weather analysis and prediction. In the Civil War, success or failure was only one unpredicted cloudburst or winter storm away.

J.K. Trammell, Ph.D., is chair of sociology, criminal justice, and human services at Mount Saint Mary’s University in Emmitsburg, Md. He specializes in social history, the slave trade, and disability. He can be reached at

This story was posted on on April 28, 2020.