You just never know. I wouldn't plan on it, but if you leave a couple flexible afternoons without ADRs or park plans that you don't want to change, then you can head over to a water park if the weather is right. In early February last year, we had a great time at Typhoon Lagoon with the weather in the high 70s/low 80s.
I've been to WDW in November and December and I was fine swimming then. However, I'm from the northeast and have seen people here put shorts on when the temps hit 50 degrees. Many of us drink iced coffee year round too. In other words, cold to us is not the same as cold to someone from a warmer climate.
We've gone in January alot. We have had wonderful cool days with jeans and tshirts. We have had hot and sunny days with shorts and pool time. We have had frigid days with winter coats, hats and gloves. It's the one time of year we have to pack it all .... so I would never know until I got there.
If it is a hot and sunny day - why not? Bound to not be crowded, slide after slide with no wait. You might be done in half a day