Cleveland zoo is like many northern Zoos in that they shut down most places to eat or get a drink in the winter time. We did not go in the rain forest because of running out of time, but that indoor restaurant is usually open year around!
Animals are usually more active in cooler weather rather than hot weather. Cool weather means more active pictures than dragging around ones! Of course, some animals may still be dragging, just cannot win them all!
When it gets really cold the wife will brace the elements while I stay warm. I am not a winter! However a cool day is well worth your Zoo adventure and shutterbug exposures!
Another advantage for zoo cool days is that fewer people are there giving better pictures and a slower pace to get that special picture!!