Some Relations Between Air Temperatures and the Surface Water Temperatures of Lakes

An analysis of meteorological and hydrographic records collected at South Bay, Ontario, over the past nine years shows that when the monthly mean surface water temperatures for successive years are plotted against the monthly mean air temperatures, the general relation can be described by two linear regressions. One of these lines corresponds to the May–July period in which the temperatures rise, while the other covers the August–November period in which they fall. A quite comparable picture is also obtained for Lake Opeongo, Ontario, and Lake Mendota, Wisconsin. The latter bodies differ markedly from South Bay in morphometry and location. Lakes Opeongo and Mendota have continental situations, whereas South Bay is enclosed in a comparatively small land mass which in turn is surrounded by very large water masses.