Ok, so I know that deep water holds cooler temps in the dog days of summer. But in the winter when it's cold outside, say Dec and Jan. When the shallows are cold does the deeper water hold warmer water? Or do fish just find structure in the shallow water that hold heat? We don't have a lot of rocks (that I know of) in the 2 lakes I fish, But we do have a ton of stumps, stickups, and hydrilla. All of these retain heat I believe. Sorry for all of the confusion , I just want to know what to target when it gets cold. shallow cover and structure or deeper water. I realize it will be a while before this happens, but I am trying to plan a winter fishing trip for a few days.

If the lake you are fishing is deep enough and it thermoclines in the summertime, then the fall turn-over will mix both top and bottom waters, creating an equal temperature throughout the water column.

If the lake you are fishing is deep enough and it thermoclines in the summertime, then the fall turn-over will mix both top and bottom waters, creating an equal temperature throughout the water column.

... and then, after some time, the warmer water will be in the lower column. And that will be were you find the majority of the fish.

If there's stumps and hydrilla the fish here in Florida usually hold tight to the stumps or just under a matt of hydrilla. If you have open water they'll suspend and move up and down in the water column depending on available sunlight.

I found this tidbit about water temps:

"Water is most dense at 3.98 °C (39.16 °F) at standard atmospheric pressure. Thus as water cools below 3.98 °C it decreases in density and will rise, the most obvious example being that ice floats. As the temperature climbs above 3.98 °C, water density also decreases and causes the water to rise, which is why lakes are warmer on the surface during the summer. The combination of these two effects means that the bottom of most deep bodies of water located well away from the equatorial regions is at a constant 3.98 °C."

Bigtimfish, looks like you are from Texas, the water temperatures shouldn't get down to the freezing point, maybe 45 degrees core water temperature.

Bass are sunfish and will seek the warmest water with good dissolved oxygen levels; comfort range is between 40 to 80 degrees, DO levels between 3 mg/l to 12 mg/l. Water colder than 39.4 degrees has too high of DO, water above 80 is generally too low DO levels depending on wind and weed cover. The bass will go into colder or warmer water for short time periods.

Florida strain LMB are not as tolerant as NLMB to cold water temperatures; 45 degrees is about the lower limit, 85 the upper limit.

LMB can be anywhere in regards to depth during the cold water period if the DO and temperature limits are within their limits. Deep water is usually warmer than cold surface water due to springs in smaller lakes and current in larger lakes.

Use your electronics to locate baitfish, look for diving grebes (birds) feeding on bait. Also keep you eye out for bass feeding activity, both on the meter and surface. Structure spoons, drop shot, jigs, swimbaits are all good cold water presentations, where I fish.

WRB

During winter green Hydrilla will hold heat and give off oxygen making it an excellent target for winter bass.

3 or 4 days of cloudless skies will warm up the shallows provided the nights are not too cold or the wind is not to strong; cloudy days following sunny warming days will retain the heat.

Deep water structure is less affected by cold fronts and should always be your #1 target during winter.

Don't be fooled into believing bass will not chase fast moving lures because Rat-L-Traps are deadly during cold water period.

The post with the tidbit about water density and temperature is helpful.  To put it in a more general term is this...in the warm months the warmer less dense water "floats" on top of cooler water. But a point, as the top layer of water cools (in the fall) it becomes colder (denser) than the bottom water. Thus starting the "turn over effect" fishermen dread and complain about. The top water which is now cooler sinks and the bottom water which is warmer rises. Now as the new top layer freezes the ice actually insulates the water below it, keeping it from freezing. So, a lake of decent depth never freezes solid. The water temperature would actually rise as you got deeper (moving farther from the ice that is), since it is being insulated. The temperature at a certain depth should be around 40 degrees and stay that temperature to the bottom. This depth would depend on many things (air temp, elevation).

We really take for granted what a unique compound water is. It is the only substance that the solid state is less dense than the liquid (which is why ice floats otherwise lakes and oceans would freeze solid). It takes more calories of energy to change the temperature of water than any other substance, which makes it a most stable environment to live in. If it weren't for these properties life would not exist on Earth...unless you believe in Creationism and not Evolution,