In 映画 3-7, they only showed the kids in Hogsmeade during the winter (there's only one scene per book that was actually relevant to the plot, and it just happened to be in the wintry-months). In movie 8, Harry and the trio arrive in Hogsmeade in May, and there's no snow on the ground.
In the books, they go a couple of times during the year, and there isn't always snow on the ground.
