 If you enjoy fishing Wyoming's lakes and reservoirs across different seasons, you probably notice a wide range of temperatures. The most obvious is a formation of ice, but many lakes and reservoirs also experience turnover in the spring and fall. The waters of large lakes in temperate regions of the world are generally separated into distinct temperature layers. This is known as thermal stratification. Lakes become stratified during the summer and winter. During the summer, the top layer of lakes warm with the sun's heat. The lowest layer remains cold. In the middle is a layer of rapid temperature decline. Along with temperature, water density falls the same pattern, with lighter water on top and denser water on the lake floor. Fall turnover occurs when the surface water begins to cool and sink, aided by strong fall winds and the lake temperature becomes more uniform throughout. As winter sets in, ice covers the lake. Ice is very low density, which is why it floats. The winter temperature stratification results in the coldest water on the top of the lake just below the frozen ice and a subtly warmer layer deeper in the lake. As ice breaks apart and wind picks up in the spring, stratification is broken and the waters mix again. Temperature and lake stratification are major drivers in aquatic systems. Lake plants and animals are dependent on and adapted to this seasonal cycling. So the next time you're out fishing, consider how lake stratification or turnover might affect where you find your next catch. For the University of Wyoming Extension, I'm Milton Geiger, Exploring the Nature of Wyoming.