I think the hardest thing is making people believe it beyond just looks. You know how in Oblivion NPCs would talk to each other? And how they always only talked about how disgusting mudcrabs are? It would be nice to see them actually discuss the weather, even if it is cliche. Using my month by month example, in the month leading to spring an NPC may say: "It's finally warming up, I could have sworn my toes were gonna fall off." In the month of spring he may say: "It's been really nice out lately, maybe I'll close my shop for a weekend and head out to my cabin." And finally, as it gets close to summer he would say: "Whew! It's definitely warming up outside, I wonder if it will get as hot as last year."
The only problem is I KNOW Bethesda won't do that, it would take too much time, effort, and unique voices