Frank Darabont, writer-director-producer, on season 2:
"It would be great not just to get out of the heat, but to present a different idea to the audience visually and tonally by having it be winter. There's some really cool stuff that [the comic's writer Robert] Kirkman did, where they find the one zombie that's frozen to the ground. I’d never seen that before and that's really cool."
"Or when [the character of] Michonne shows up -- and boy, is she a character I can't wait to get to -- when she comes striding out of the wasteland like a Clint Eastwood f***ing spaghetti western character cross-melded with some samurai movie, like the Baby Cart character with the f***ing sword, and there’s just a little drift of snow in the air. I would love to put that on film."
Update (2 Sep 10): Unfortunately, this news has been debunked as a rumour by Darabont himself, speaking to AICN.