Column Editors’ Note: Historical weather and climate data have become essential resources for tracking and understanding global warming. All too often, however, these data sets are treated as inert and apolitical. In this column, Elaine LaFay shows that historical weather data reveal far more than a changing climate: they play a key role in American settler-colonialism in the context of U.S. expansion into the Gulf South. Winds and weather were understood as active participants in human health and as powerful instruments in settlers’ imagination of themselves and their world.

Keywords: weather, climate, empire, meteorology, diaries, observation

Weather diaries are a curious artifact. In contrast to contemporary data sets and computational tools of statistical analysis, 19th century examples show how data in the past was deeply affective and mediated by individual, embodied experience. They can nevertheless be semi-reliable archives of weather: historical climatologists have aligned weather diaries of the past with proxy records from tree rings, ice cores, and soil samples to limn climate change in the last millennium, and in Europe and North America, since the Little Ice Age in particular (DeGroot, 2018; Slonosky & Mayer-Jouanjean, 2020; White, 2017). These scholars have mined past weather journals for insights into how people experienced, and adapted to, changing climates, often with an eye to how these adaptations can inform our response to our own planetary emergency (Edwards, 2010). The practices of weather observation and meteorological data-making have a long history. In the early modern era, meteorological diaries were a proliferating genre among colonists, enslavers, industrialists, natural philosophers, and everyday people. The practice of weather journaling rose to prominence in Europe by the late 17th century, and by the 18th century it was a popular habit of bourgeoisie life.

Meteorology was also a tool of empire. As white settlers poured into French and British colonies, weather diaries became more abundant in those settlements as well. Knowing that the climate was a high-stakes extension of empire, colonists used such knowledge to advance claims not just to the land and its use but also regarding the Indigenous peoples who already lived there. In other words, climatic knowledge informed colonial orientations toward places colonists already believed to be theirs. Chronicles of local weather were among the first data sets new settlers circulated to the metropole, which has left contemporary scholars with a vast resource of individual collections of weather observations (Zilberstein, 2017). Weather diary keeping was not restricted to the scientific elite. Anyone with time, leisure, literacy, and a modest interest in the broadly conceived genre of natural history would be qualified to start a weather diary; often, annotations of the weather featured meteorological charts alongside longer descriptions, or would appear casually within letters, travelogues, almanacs, and agricultural pamphlets.

Weather journals knitted together historical actors who would otherwise have little in common with a shared practice of observation. Weather instrumentation became increasingly available over the 17th and 18th centuries, and by the turn of the 19th century thermometers (for temperature) and barometers (for atmospheric pressure) were accessible to most middle-class homes. Some weather diarists noted nothing but the temperature or direction of the wind. Others, like French migrant Peter Legaux in 18th century Pennsylvania, had an array of instruments at their disposal. Legaux’s weather diary for Spring Mill, a town outside Philadelphia, had space for the use of a thermometer to note the mean temperature in both Fahrenheit and Reaumur degrees; a barometer; udometer to measure rain or snow; anemometer for wind direction or speed; “magnetical” to measure magnetic variation; hygrometer for humidity; in addition to spaces to measure the height of the river, notes for “prevailing sicknesses” and remarks on “vines and grapes,” “grain and trees,” “birds and insects,” and “births and deaths” (see Figure 1). Producing meteorological data in the 18th century was also to produce data on life, death, and the more-than-human phenomena of the world.

Nor did weather observers merely produce data once a day. Sometimes they recorded temperature up to five times a day; Legaux, twice. Thomas Jefferson, a devoted weather observer, detailed when and how these data sets should be produced in a letter to James Madison in 1784: “1. day of the month. 2. thermometer at sunrise. 3. barometer at sunrise. 6. thermom. at 4. P. M. 7. barometer at 4. P. M. 4 direction of wind at sunrise. 8. direction of wind at 4. P. M. 5. the weather viz rain, snow, fair at sunrise &c. 9. weather at 4. P. M,” as well as other columns on local flora, fauna, and astronomical events like eclipses (Jefferson, 1784). If Madison did not possess any instrumentation for his not-yet-started weather diary (he did not), Jefferson added, he ought to get a thermometer and barometer post haste. By the late 18th century, observers could fill in weather observations in ready-made tables with room for each instrumental data set and personal commentary. While weather diaries vary in content, many in the 19th century adhered to some degree to this formula: a blueprint for what the citizen-scientist needed to know about a place to understand it. For many, the task of weather journaling carried the assumption of leisure time, made possible in the case of Jefferson and Madison by reliance on enslaved labor.

Weather diaries reveal prevailing understandings of the weather and the relevance it had in daily life. Even beyond historical record-keeping, this data had other epistemic and political purposes. Meteorological journals are a window into ways of experiencing weather that rely on both embodied sensation and technical data collection, and one answer to the question of how to know a place, both from within and afar. Jan Golinski (2007) has shown how the rise of weather journals in 18th century Britain represented an attempt to bring weather observation out of the realm of lore and superstition and into an Enlightened epistemology of disembodied reason in a universe run by natural laws. But even as new instrumentation allowed weather observers to make ever more precise measurements of different atmospheric phenomena, embodied knowledge persisted. This was not least because people believed that the weather had tremendous agency for health and illness, and knowing the prevailing weather patterns informed the everyday pursuit of healthy living as well as more formal medical practice.

Weather observers studied their climates with deadly earnest. Physicians of the early modern era were as skilled in meteorology as in treating disease, and often the two were one and the same. Indeed, one of the duties of boards of health during epidemics was to carefully track the weather and publish their observations each day. Since the ancient Hippocratic treatise Airs, Waters, and Places posited a link between prevailing climatic conditions and local diseases, early modern weather observers knew that weather had implications for their health (Hippocrates, ca. 4^th c. B.C.E./1849; Golinski, 2007; Harrison, 1999; Valenčius, 2002). The project of health was above all a project of balance: balancing the humors of the body in accordance with its surroundings. Watching with alarm the rising cases of putrid sore throat in Charleston, South Carolina in 1813, Charles Watts wrote his sister Helen that “the weather has been open and wet, and consequently favorable to this epidemic.”1 People like Watts knew that certain weather conditions could foster pestilence more readily than others, or that some winds were more likely to mix with fetid soils, stagnant pools, and decaying organic matter to produce miasmas, disease-carrying agents in the air.

Even when observers had access to cutting-edge meteorological equipment, the lines between instrumentation and embodied knowledge blurred. In this era, knowing the difference between a miasmatic wind, a fetid marsh, or a health-giving atmosphere, relied on bodily and sensory knowledge that was not so easily displaced by the quantified readings of instruments. Indeed, the body itself could be an instrument. One popular medical guide warned its readers of the risks of staying indoors all day, becoming “so delicate, as to feel even the slightest changes in the atmosphere, and by their pains, coughs, and oppressions of the breast, &c., they become a kind of living barometers” (Buchan, 1793, p. 86). What did it mean to be a ‘living barometer’? How would such a person have encountered the atmosphere around them? The boundaries of ‘atmosphere’ were more fluid than fixed, and sometimes extended into the cosmos: even as astrology lost the centrality it once had to medical practice by the 19th century, in 1829 one practitioner was still able to observe in a medical textbook that there may yet be “more in medical astrology than is, perhaps, generally supposed” (Good, 1829, p. 109). In the 19th century, disease was understood as a process, not a discrete thing; it was the process of a body out of balance with its broader environment.

Data, as Lisa Gitelman (2013) and others have argued, can never be ‘raw.’ Rather than regarding data as an inert, static object that is passively collected or found, scholars have shown how data is made in cultural contexts that show its ties to diverse and sometimes conflicting ambitions. An array of peoples and institutions, including military physicians and scientific societies, tracked weather data across the early modern era and into the late 19th century, by which point it had become formally tethered to forecasting (Carson, 2021; Pietruska, 2017; Valenčius, 2002; Zilberstein, 2017). Perhaps the most robust group producing weather data were those participating in what we might today call vernacular meteorology, in which ordinary citizens recorded the weather for its relevance not just to health but also to agriculture, business, travel, and empire.

Weather Observation as Imperial Science

Settler meteorologists in the United States were part of a vast network of weather observation that stitched professional concerns with weather to imperial priorities. It was the ambitions of empire that animated the shift from 18th century vernacular meteorology to the ‘dynamic climatology’ of the 19th century, in which climatologists within the landlocked Hapsburg Empire developed a multi-scalar research program to understand climate over large distances (Coen, 2018). In the Indian Ocean, cyclones emerged as an object of scientific curiosity because of the British imperial imperative to prevent shipwrecks and protect revenue from sudden tropical storms (Bhattacharyya, 2022). Through storm narratives, ship logs, storm cards, and weather observations, Victorian weather scientist (and coiner of the term ‘cyclone’) Henry Piddington sought to “achiev[e] a discernible order in the stormy skies” and use climate science to take on the problem that tropical storms posed to imperial trade routes and insurance markets (Bhattacharrya, 2022, p. 166).

In the United States, recording weather data was part of an imperial project that extended throughout the structures of settler colonialism. The violence of dispossession, building on and cultivating stolen land are the most well-known faces of settler colonialism, but the construction of scientific institutions and the practices of everyday citizen science are part of the same imperative. In part, this was a practical endeavor: settlers wanted information on the places they colonized. When the enslaver and astronomer William Dunbar of Natchez, Mississippi, circulated his weather data in 1809, he clarified in the title that its purpose was “to give some idea of the climate of that country” (Dunbar, 1809, p. 43). Weather observers circulated weather data often with the explicit goal of informing potential white settlers. Excerpts from such diaries often appeared in emigrant guides, so much so that one publication reviewed weather data from several guides at once, declaring that, “At a time when the health and comfort of so many of our emigrant countrymen depend on a correct knowledge of the climate of Canada, and of the United States, the subject cannot be too attentively investigated, or too minutely explained” (“On America,” p. 120). In a letter to Dunbar, Creole natural philosopher Barthelemy Lafon introduced his meteorological observations from New Orleans and added, “It is greatly to be desired for the advancement of the sciences that there should be a scientific paper here in which the observations and discoveries of the country would be recorded” (Lafon, 1805.) Weather observers knew that they contributed to an Enlightenment imperative of building scientific institutions that centered the newly minted United States as a legitimate site of knowledge production. Dunbar himself was a devoted weather diarist and sent meteorological observations regularly to Thomas Jefferson during his presidency (Dunbar, 1804).

Using slave labor, Dunbar ordered an observatory built on his plantation that he proudly opened to the public. Armed with a thermometer and barometer, Dunbar calculated the monthly averages of temperature, atmospheric pressure, and rainfall, which featured on the front page of his “Meteorological Observations” to the American Philosophical Society (APS) in Philadelphia. Yet the bulk of his text was not in charts, but in prose, illustrating the centrality of qualitative and quantitative data taken together. Painstakingly, Dunbar described each aspect of the Natchez climate from his plantation “The Forest,” explaining extremes of temperature, noting the direction of the wind during each month and its implications for planting crops, the labor of the people he enslaved, and the ebb and flow of seasonal fevers and ague. In February, he basked in the sublime vista of a snowy forest: “The sun peeps out, and a moment is granted to admire the most enchanting of pictures” (Dunbar, 1809, p. 44). In March, the people he enslaved planted cotton, but Dunbar simply wrote, “Planted cotton,” excising their existence from his record-keeping until August, when enslaved people picked up to “80 to 140 lb.” of cotton each in the “unusual heat of the season” (Dunbar, 1809, pp. 45, 46). The descriptions reveal how Dunbar intended his meteorological data to be of use: to northeastern men of science (the presumed audience at APS) who sought to bring a far-flung part of their country into their intellectual purview, and by enslavers and natural philosophers with an eye to migration. Enslavers’ data, as Caitlin Rosenthal (2021) has shown, answered enslavers’ questions.

For Dunbar, the collection of meteorological data was inextricable from the political project of growing the slave regime. In 1804, Jefferson sent Dunbar to join the physician and metallurgist George Hunter at the helm of an expedition along the Arkansas Red River. It was the first federally financed scientific expedition in the newly purchased Louisiana Territory (Strang, 2018; Valenčius, 2002). At least two enslaved people and several more soldiers accompanied the expedition. In preparation, Dunbar insisted on two thermometers (in case one broke), a portable barometer, and several other instruments for measuring latitude and observing the heavens. Packs laden with weather instruments do not generally feature in how we imagine colonial exploration, but no expedition was complete without them. Dunbar dutifully began each journal entry with the temperature of not just the air but also of the river, and observations of sky and fog (Figure 2). As on Thursday, November 1: “Calm—clear above, a little fog on the river” (Dunbar, 1809, p. 1). Moving carefully up the river, Dunbar and his company journeyed past a mélange of Indigenous nations, French and Spanish settlers, Dutch hunters, and slave labor plantations. All the while they calibrated instruments, marked latitude, took the temperature twice a day, and chronicled the flora, fauna, and peoples they encountered. As Conevery Valenčius (2002) and Cameron Strang (2018) have pointed out, for Dunbar and the physician who joined him, the task of a scientific expedition was the extension of American knowledge-making as authority. In the pursuit of this data, Dunbar and Hunter contributed to a larger intellectual project of normalizing Indigenous dispossession and sought to secure the place of American science in the international arena. They and other weather observers asked, what did it mean to have an American climate? The violence of settler colonial dispossession lay in the question itself.

Weather journals are dusty sources, yet they brim with life. In the charts and tables of meteorological observations, we can glimpse a world in which observers attempted to contain the tempestuous, unruly weather of the world in clean ordered lines. Weather journals offer a window into a moment when the risks and benefits of one’s surroundings could be written on the body, in the shadow of a spleen or the fluttering of one’s nerves. When we read sources like weather diaries for more than the data alone—when we read the frame, as Rosenthal (2018) argues, in addition to the data itself—we can see how data was also affective and embodied. We can also see how this data was political in ways that show its ties to American imperialism and slavery, underscoring how 19th century regimes of quantification were never simply exercises in austere data collection. Meteorological data was never collected: it was made. For citizen scientists of the bourgeoisie in Europe and North America, weather journals were associated with gentlemanly leisure and a scholarly interest in the prevailing climate. But weather journals are also archives of imperial science, places where the dogged production of data not just informed military projects and the uptick in white settlement but secured the role of scientific knowledge production in the American empire.

Disclosure Statement

Elaine LaFay has no financial or non-financial disclosures to share for this article.

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©2023 Elaine LaFay. This article is licensed under a Creative Commons Attribution (CC BY 4.0) International license, except where otherwise indicated with respect to particular material included in the article.