Hiya Liyuan!
Welcome to planDisney! Walt Disney knew what he was doing when he started work on "The Florida Project" which soon became what we know now as Walt Disney World Resort. Florida's nickname as "The Sunshine State" is confirmed by its year-round sunny weather that ranges from warm to hot like the sun. Yes, I said it, Florida does get hot and you will find it's a lovely temperature in January.
Disney's Art of Animation Resort has no indoor pools but
three heated outdoor pools named The Big Blue Pool, Cozy Cone Pool, and Flippin' Fins Pool. The water is heated to approximately 80°F which is about 27°C. Once you make it inside the water, no matter what it feels like outside you will find it very comfortable. I have enjoyed the pools at Walt Disney World Resort on cold days and my top tip is to make sure you have a dry towel ready to be wrapped around you as soon as you get out of the water as that chilly air can be a shock! Thank goodness there are free towels for guests located by the pool. Did you know that The Big Blue Pool is the largest pool on the property? You can imagine yourself as Nemo cruising along with his friends in the ocean.
Disney's Blizzard Beach Water Park is open for your enjoyment even if it may be chillier than you would prefer. I don't know your weather tolerance but in January, temperatures in Orlando, Florida range from a high of 76°F (24°C) to a low of 57°F (14°C). My research shows that it will be a pleasant diversion from the much colder temperatures you might feel in Hertfordshire. I'm sure that midday the weather will be perfect to enjoy the slides and pools at this water park. The water here is also heated as well so you can do what I do and just stay submerged to the chin in the water and float till the stress leaves your body.
I hope you find time to float free and happily on your upcoming trip and if you have any more questions please
let me know!
Happy Planning!
-Nimmy