The water temperatures are tied to the amount of sunlight the water receives. Unless there is some geothermal hot springs feeding a lake the main source of heat is the SUNLIGHT!

You block out the sun and the water will chill really quick.

Heat radiates off the water especially at night when there are not clouds to keep the heat in. This cools the water each night. Not until the sun pops up the next day will the water warm up.

You might say that water temperature is a record of the average amount of sunlight over the past few days. That's because of the specific heat of water. It take a while for water to warm up and it also takes a while for water to loose it's heat.

If more heat is added on average over a 24 hour period of time then the water will warm up a degree or two.

It all depends on the latitude of the lake and the amount of solar radiation hitting the water.

Quote Originally Posted by mrobertson View Post
i do not think fish relate to water temps as much as people think. Icon we are talking about the spawn, but in general I think they relate to the amount of day light. Here is an example in August the water temp could be in the 80's and the fish shallow not deep. You would think with hot water temps they would stay deep but they dont. granted water temps do effect fish a little, i think the fish know when it is time to do something by the amount of daylight, long days short days. In the spring they go shallow in the summer they go deep and in the fall they come back shallow. I think the fish spawn in a period where the days are getting longer and that is a 2 or 3 month period.