I do not recall seeing much snow or any serious weather change in the Walking Dead series. Is there a specific reason for that?
Recently, The Walking Dead executive producer Gale Anne Hurd was asked about the frequent lack of changes in the weather on the series by Access Hollywood, and let the outlet in on a little secret; the lack of seasons totally has to do with the drama’s production schedule.
"Yeah, it's dependent on the weather when we shoot."
It’s not likely we’ll get to see a winter wonderland on the show anytime soon, although Hurd also tells Access Hollywood that she would love to see snow in the cards should the show be able to finagle it.
"We do shoot right up until Thanksgiving, so if there is an early snowfall in Georgia, we'll be happy to capture it."
Taken verbatim from this website
I think it's mainly because winter is more of a danger to the cast. Ice can form on the ground and cause some people to slip and put themselves at risk of serious injuries not to mention it's easy to fall ill in those weather conditions meaning a cast member gets sick they have to postpone shooting until that member recovers fully and then everything gets set back.