# Is it possible to find the temperature at the center of a lake if you know the temperature of the wa **URL:** \ **Category:** Factual Questions\ **Created:** [October 18, 2016, 12:23pm UTC](https://boards.straightdope.com/t/is-it-possible-to-find-the-temperature-at-the-center-of-a-lake-if-you-know-the-temperature-of-the-wa/768937 "2016-10-18T12:23:30Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [October 25, 2016, 5:10pm UTC](https://boards.straightdope.com/t/is-it-possible-to-find-the-temperature-at-the-center-of-a-lake-if-you-know-the-temperature-of-the-wa/768937/21 "2016-10-25T17:10:52Z")
Let’s go back to that surface map of Lake Michigan. I am quite surprised at the 20 degree difference from 36 degrees to 56 degrees near the center of the Lake. Explanations? ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [October 25, 2016, 7:04pm UTC](https://boards.straightdope.com/t/is-it-possible-to-find-the-temperature-at-the-center-of-a-lake-if-you-know-the-temperature-of-the-wa/768937/22 "2016-10-25T19:04:18Z")
> [@PastTense](#): > > Let’s go back to that surface map of Lake Michigan. I am quite surprised at the 20 degree difference from 36 degrees to 56 degrees near the center of the Lake. Explanations? In October in the N hemisphere, the surface temperature will obviously on average be higher than the deep water temperature. I think that the areas with much lower surface temperature must have convective (or more precisely, advective) flows bringing colder deep water to the surface. ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [October 25, 2016, 7:52pm UTC](https://boards.straightdope.com/t/is-it-possible-to-find-the-temperature-at-the-center-of-a-lake-if-you-know-the-temperature-of-the-wa/768937/23 "2016-10-25T19:52:11Z")
The temperature map the **PastTense** asked about was from ~6:00 am (a wonderfully appropriate name-post combo); if you click the link now you get an 11:03 map and the cold spot has moved to the northeast. I think it’s more surface currents than vertical mixing. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [October 25, 2016, 8:15pm UTC](https://boards.straightdope.com/t/is-it-possible-to-find-the-temperature-at-the-center-of-a-lake-if-you-know-the-temperature-of-the-wa/768937/24 "2016-10-25T20:15:24Z")
> [@Enginerd](#): > > …I think it’s more surface currents than vertical mixing. I don’t understand what you mean - how can (lateral?) surface currents _give rise_ to large surface temperature differences? ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [October 25, 2016, 9:05pm UTC](https://boards.straightdope.com/t/is-it-possible-to-find-the-temperature-at-the-center-of-a-lake-if-you-know-the-temperature-of-the-wa/768937/25 "2016-10-25T21:05:14Z")
> [@joeytk7](#): > > the lake i am referring to is a small lake with the deepest point around 14 feet and only around 80 acres in area. When the wind blows, does the lake mix all as one body, or as two or three stratified cells? If there is complete overturn, for a significant amount of time, then the surface temperature will more or less be the temperature of the whole lake. Unfortunately, water doesn’t like to mix with water of a different temperature (you can check that out in your bathtub). So the greater the difference between the temperature at the surface and the temperature at the bottom, the greater the number of stacked mixing cells when the wind blows. There will be some heat transfer, but the larger the number of cells, the more heat transfer will be impeded. There is no measurement you can take on the surface that will predict how many cells are likely to form. > [@Czarcasm](#): > > What other factors, specifically? One I didn’t see listed (but may have missed) is how turbid the water is. In clear water, sunlight can reach down more than, say, twenty feet. In turbid water, all of the sunlight, and therefore all of the radiated heat, is absorbed in the first few feet. > [@Enginerd](#): > > You need to have more than just the shoreline temperature for all time. In a lake that size,\*\* the greatest heat flux is going to be at the water surface\*\* - . . . > > Or you could get a boat and a thermometer. It’s both more practical and more fun. The ratio of the surface area to the volume of the lake matters a great deal, too. The deeper the lake, the less likely it will be that warmth from the surface reaches the bottom. Going out in a boat with a thermometer is grand. If you also have a sampler, and the lake is stratified, you’ll find different nutrient profiles at different depths. > [@Riemann](#): > > I don’t understand what you mean - how can (lateral?) surface currents _give rise_ to large surface temperature differences? Here’s one way. The wind blows across the lake. It pushes surface water from upwind to downwind. As it travels along the lake surface, it is warmed by the sun. At the far edge of the lake, that water has to go somewhere, and typically it goes down, starting a mixing cell. The water goes down until it reaches water it doesn’t want to mix with because its temperature is too different or until it reaches the bottom of the lake, whichever comes first. Then it turns and travels upwind until it reaches the upwind side of the lake, where it wells back up to the surface. While it travels under the surface, it has less contact with sunlight and is in contact with cooler water, so that when it upwells, it is now cooler. Therefore if there is a prevailing wind direction, the upwind side of the surface of the lake will be cooler than the downwind surface of the lake. Here’s another way. There’s a brisk mountain stream coming into the lake. It’s travelling fast, though a shaded area, so its water is colder than the water in the lake. While the cooler water will tend to sink, where it enters the lake it will mix with the water at the lake’s surface, causing the surface temperature there to be lower than the surface temperature in other places. Just one more way. Moonshiners could use the lake water for cooling their still. The discharge area would become a local hot spot, relatively. [Previous page](https://boards.straightdope.com/t/is-it-possible-to-find-the-temperature-at-the-center-of-a-lake-if-you-know-the-temperature-of-the-wa/768937.md?page=1)