I didn't know that it gets to cold but I guess the best answer would be like Derek 81 and Stratos G said when the water gets to hard. I think 15 degrees is the coldest I've fished in. Several years ago we blasted off in a tourament on Dale Hollow it was around 15 and the high got up close to freezing. Now we spent a lot of time dipping out rods in the water thawing out the guides. My biggest fish came in late March and my next biggest came on December the 29. The last fish of the year. Just got to layer, layer and more layers.