Part of it really depends upon what part of the country you live in-so what your idea of "warm enough to swim" is. Boy, I've seen the affect of this first hand! We used to live way up in New England and always swam at WDW in November. We'd be swimming, having a blast, while the CMs be all bundled up, looking at us like we were crazy to swim in such cold weather. Now we live in a climate that makes WDW seem cool and on my last few trips, I've looked at those same crazy Northerners swimming, shaking my head. Now I won't go in the water unless it's at least 85 degrees out. Usually that's not late November.