FnF temps

All this talk about float and fly fishing has got me all fired up! I can't wait to get back down to C-land or Dale and have at it. There is a burning question in my head, though. Why is it that the generally accepted water temp for the start of FnF action is 50 degrees? Will they not hit it in warmer temps and why? Just trying to understand the whole thing a little better.

The smallies will start to suspend at that temp the best, my personal opinion. I will start fishing the fly around 53 or 54 but really like it when it hits 50 that first time.