Hi Rhiannon!
Thanks for your question and for visiting the Disney Parks Moms Panel!
Visiting
Walt Disney World in late January is a wonderful time of year to come. The holiday crowds (and prices) are gone and the
Disney Marathon weekend has also come and gone, along with those crowds.
There is never really an "off" season at Walt Disney World any longer, but I think you will find the prices for this time of year to be quite low compared to other, more busy times of the year.
As for it being warm enough to do the water parks, I would say yes, but that is a personal opinion. I do not get cold and actually enjoy the lighter crowds at the water parks in the winter Florida months.
I hope this helps and I wish you a Magical trip!!
Chris