Temperate lakes undergo a seasonal thermal stratification cycle: strong thermal stratification (distinct epilimnion, thermocline, hypolimnion) develops in summer; this breaks down during autumn cooling, producing an isothermal, well-mixed water column during fall overturn; inverse stratification develops in winter (ice-covered, with near-0°C water at the surface and denser ~4°C water at depth, since freshwater is densest at 4°C); and spring warming again produces an isothermal, well-mixed water column during spring overturn before summer restratification begins.