Lake Water Temperatures

When they publish Lake Water Temperatures, at what level are they taking the temperature ?

I've always been curious about this.

most likely at the surface

I had assumed that the temp was taken at the surface but I never heard one way or another.

It looks like no one really does know when they talk about or hear the Lake Temperatures are X.......at what level they are really taken...it sounds good however...

I thought I was the only one who didn't have a definitive answer.