A good question. I have been wondering about it myself. Since people thought that they should drink spirits in hot weather in order to "warm up" their insides which they believed had been left weak and cold by sweating, and since little beer was brewed in the early colonial South (weak beer of less than 4 per cent alcohol by volume, as was traditionally drunk in northern Europe, would have rehydrated rather than dehydrated), it would be logical to assume that a lot of people must have died as a result (directly or indirectly) of dehydration. Definitely a subject deserving of research. Presumably you have read K. O. Kupperman, "Fear of Hot Climates in the Anglo-American Colonial Experience," William and Mary Quarterly, 3rd Series, Vol. 41 (1984) pp. 213-40. Another useful original source, if you can find it, is Richard Ligon (or Lygon), "A True and Exact History of the Island of Barbadoes" (London, 1673). There is a copy in the British Library but I don't know about the US.