Mariners, fishing vessels, and meteorologists all look to satellites to provide timely and accurate maps of sea surface temperatures—or lake surface temperatures in this case. This map shows lake surface temperatures across the entire Great Lakes system on April 18, 2006. It was created by analyzing data from the MODIS remote sensing instrument on NASA’s Aqua satellite, which measures thermal radiation emitted from the lakes’ surface.
The temperature patterns shown here are affected by latitude, lake depth, winds, currents, river discharge, and other factors. The warmest spots are located in shallow bays and nearshore waters of the southern lakes. The deep waters of Lake Superior are much colder, as is Lake Huron’s Georgian Bay.