Huge fan of the feb trips, its my fav time of the year to go (No, my birthday in feb is not my major motivator
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So far all the pp have been steering you in the right direction. It can start as cold as the 30s to low 40's in the am and climb all the way up to the 80's by mid-day. Alot of the reason Disney feels colder than the cold at home is we've got a humid chill (everything in Fl is humid) so it'll get into your bones if you stop moving long enough. We usually opt for at least 1 thing made of wool to take with us, whether it be an over sized sweater or a blanket, its usually enough to keep the chill at bay.
No matter where or when you go in Florida, no matter how grey and cloudy the skies look, you should ALWAYS wear sunscreen. As a fl native, this is something I stress to everyone. Florida is a great big magnifying glass and the clouds and even window glass don't keep the most damaging rays from reaching your skin. For the best protection, find a sunscreen with uva/uvb protection
All the pools and water parks remain open, and a great deal of the resort pool are also heated, so even if its super chilly in the air, the water should be just comfy enough to get in a quick dip. I know I've done the insanity scuffle back to the hotel room a few times when I decided it wasnt too cold (please note: it was most definitely too cold for me lol) But it was super comfy in the pool, I almost didn't want to leave the water