<p>This paper examines the unique challenges of practicing medicine by British Army and Royal Navy medical practitioners in the cold climates of colonial British North America during the eighteenth and early nineteenth centuries. I consider how army and naval medical practitioners characterised the northern temperate climate and how these perceptions influenced medical practice. Additionally, the paper illustrates the interactions between seasonality, supply and transportation difficulties, and the logistics of using local resources of wood and coal for fuel in army and naval hospitals. </p>