You do realize that although YOU may live where it's cold int he winter there are plenty of other areas where it is warm year round. The OP didn't say where she lived so there's no need to say she's crazy because YOU are projecting your circumstances on her and assuming that she's planning for something 4 months from now.
Or it could be an indoor water park (which is what I assumed when I read it).
OP - I see no problem with it (though I would mention it to their mum when planning).