Wind can change the Thermocline also,The lake that you fish on how deep is the water below the thermocline.Iknow heat will cause the disolved oxygen to not be as great at the thermocline.So it is important to know where the thermocline is at without electronics its hard to determine.I suppose you could use a thermometer,ether on a string or a electriconic probe type I think you fish hookup would be greater....