That’s definitely gonna be a locational thing. In my area (near Toronto, Canada), I’d say malls are more popular in the winter because they offer an escape from the cold and there isn’t that much to do in the winter, anyway. Summers in my area aren’t going to get hot enough to change that any time soon.
But for something like Arizona, it’s really easy to picture how that would be the case, cause summers there are murderously hot.
I wonder how such large buildings have such amazing AC, anyway? Most malls and big box stores have god tier AC.