As far as Lake Erie goes, "turnover" is not a quick or single weather event occurance.

Turnover is when the cooler water on the bottom, or lower part of a lake's water column, warms enough for it to mix with the upper water in the water column. In the fall it's the reverse.

Colder water is denser than warmer water, so the cooler water will be found on the bottom. When the water starts to warm in the spring, the surface water warms first, gradually warming the deeper water as the season goes on. The transition from warm to cold water is called the Thermocline. In the shallow Western Basin of Lake Erie, this process has taken place usually by about right now, the end of June. I've scuba dived in western Lake Erie in May and June and seen thermoclines at 6-8 feet off the bottom all the way down to 6 inches off the bottom.

Single day weather events don't have much, if any, significant effect on this process, with the exception of a big wind blow, which causes currents and helps move tha waters around right at the transition time. Once the water column is all within a few degrees of the same temperature, the water column will "mix" easily during wind events.

As you may expect, the deeper waters mix last (usually), and the central and eastern basins do not completely mix at all (summer thermocline down around 20 feet or so, and I've dove the central basin sunmmer thermocline and the transition is a real shock, going from over 70 degrees to 50 or less degrees in 5 feet).

From this point on through the summer, there is no thermocline in the Western Basin, so water temperature isn't as important as in the other two basins.

West