It's very common to confuse seasonal events in lake systems. Turnover refers to a substantial mixing of water within the vertical water column, and is tightly regulated by air temperature.
The general rule is, twin turnovers ONLY occur in lakes that completely ice over. You get one mixing event at ice breakup, and the other just prior to icing over.
Few Texas lakes freeze over, so they have a single turnover period, which we call "early winter." Air temperatures drop, cooling the surface water enough to make them sink. This disrupts the summer stratification regime and poof! you get vertical mixing. On the simplistic level, the waters stay all mixed up until the air temperatures heat up again in late spring. Warm water is much harder to mix than cool water, and density-defined layering sets in.
Now bloom events are very commonly mistaken for turnover events, and can be just as equally responsible for occluding the water. Seasonal Texas blooms you CAN get twice a year, one in late spring and the other in the fall. The "Spring Bloom" is almost always bigger, and is created by the combination of winter-introduced nutrients (via turnover) and increased light and warm temperatures from the spring. Diving in late springtime is thus inherently bad just about everywhere 'cept the tropics. The autumn bloom is caused by increasing mixing of nutrients brought about by cooler temperatures... or the humble beginnings of your true turnover. This bloom will persist until you get ice cover, or in Texas it doesn't really ever stop... it's more of a slow agonizing thing that drags on all through winter until the sunlight-induced bloom in late spring. That's why it's hard to get clear vis in Texas lakes during the winter, you have to find one that's "pooped out of nutrients."
And don't forget wind. Wind is stronger in the winter, and maintains mixing events. Shallow lakes and estuaries tend to be permanently mixed due entirely to wind.
Don't forget rainfall either. This does all sorts of complicated things to your lake (which I really do NOT want to explain), with the end result of it being cloudy. Rainfall in Texas is seasonal.
Sediment type, groundwater exports, and human activity also influence both blooms and water turbidity. And oh great, some of these tend to be seasonal too!
So when it all boils down, unless you're a limnologist with nothing better to do except nitpick a particular lake, wait for clearer waters in Texas lakes to show up in mid summer (june/july), and persist through to early fall (mid-October). These dates are for central Texas.
Bleah, nutrient dynamics makes my head hurt.
