Bellaire always has a winter holiday festival at the park by the police station in December. I believe it s called Holiday in the Park . and I think it has fake snow, but maybe not. Another event that I know of that usually has fake snow that s not necessarily in Houston is Dickens on the Strand in Galveston.
Galleria mall has fake snow each hour. And discovery Green,And the woodlands mall. call first just to confirm the details.
Don t they usually have something downtown around Christmas break? I would guess a call to the city switch board or the Chronicle might get you an answer.
They used to have something like that every year at Bayland Park. Look into that.Good luck!