I am conducting a pilot ethnographic project on the role of epidemiological knowledge in India in the context of climate change. Humanities researchers have rapidly scaled up their engagement in issues of climate change, in a time when human impacts on the environment have taken on new political significance. Concurrently, epidemiologists have intensified their questions of the relations between climatic shifts, weather-related disasters, and burdens of morbidity and mortality. The global health outcomes at stake in this context transcend matters of the infectious and the chronic. They are, as Bruno Latour has written, questions about the politics of nature: how nature (and its turbulence) inflects the practices of research and knowledge gathering. As such, numbers serve as more than mere proof; they also tie together diverse actors and agendas. Epidemiology is the science of disease distribution and causation is one of the key sites to assess the cultural, political, and social dimensions of such ties. As a medical anthropologist of urban India, I plan to situate my ethnographic research in the context of a climatic phenomenon that literally suffuses all forms of life in Mumbai: the monsoon. I am broadly interested in the practice of epidemiologists during the monsoon, when health statistics circulate as front-page news and become matters of everyday conversation. I am also interested in the very local work that Mumbai's epidemiologists do: they must speak for the city in relation to India's broader health statistical trends, but must also make claims about what makes Mumbai unique in terms of collecting and reporting disease data. This project thus examines how experts in Mumbai understand and express the relationship between health and the environment. Ultimately, this project will offer a grounded, ethnographic, person-centered account of the emergent field of global environmental health, while it also will narrate the story of India's epidemiologists in action.