The Deserts, Forests and Oceans regions should be fine in winter. Deserts and Oceans are mostly indoors besides the sea lions, seals and walruses that can handle cooler temperatures, the macaques (unsure on them) and the new tortoise exhibit that will probably be closed. Forests has a few tropical species that may be off-display (Kangaroo Crossing, gibbons) but also a lot of cold-hardy species like Amur tigers, grizzly bears, eagles, red panda, and so forth, as well as indoor viewing for orangutans, chimpanzee, and crocodilans, so you shouldn't miss those.
A local can probably give a more detailed answer, but given the African Plains area is entirely outdoors with no indoor exhibits visible to the public, and many of those species are kept inside at other zoos from as high as 50 F, I expect you would have a slightly subpar winter experience and rate accordingly. I made a winter visit to Omaha and even though a lot of their African species were still outside, it can still change the 'feeling' just to be missing giraffes and ostrich, for example, especially in a large mixed savannah space.