What is it?
Temperature is a measure of how warm or cold the water is. This influences what types of fish and bugs are present in a river or lake. Temperature also influences how water mixes in a lake.
Sometimes lakes can have distinct layers of water with different temperatures. This is called thermal stratification.
Thermal stratification in lakes typically follows a seasonal pattern. However, lakes of different sizes and in different climatic regions will have varying levels of mixing. For example, shallower lakes do not stratify in the summer. In colder climates, some lakes may not warm above 4°C and will only mix once in the summer; others may remain covered with ice year-round.