Decades ago I was reading a blurb in MAD magazine in which it was said that in every sitcom, the weather is always nice and sunny and warm, except for the yearly Christmas episode in which it was snowing. Decades of observation have born this out. The fact that most shows take place in SoCal probably accounts for much of this, but I suspect that budget constraints and difficulty shooting contribute something as well. And for most sitcoms, the weather really isn’t part of the plot. If it does rain or snow, then it’s because there’s going to be a joke about the rain or snow.
Are there any sitcoms (or dramas, or whatever) that show gratuitous inclement weather? That is, it’s snowing and it has absolutely nothing to do with the plot? Here is my list of these shows:
Northern Exposure, House, M.D., Smallville, Kung Fu: The Legend Continues and any of the other shows filmed north of the Mason-Dixon line (especially those filmed up in British Columbia) usually have some snow or rain that exists but doesn’t get commented upon.
The occasionally funny Christina Applegate vehichle “Jesse,” which ran on NBC for a couple seasons in the late '90’s, was set somewhere in upstate New York. There was snow on the ground most episodes and characters typically bundled up when they went outside.
Whether there’s snow or not depending on where the show is filmed makes me think that cost is indeed a large factor. It’s costly to make it snow in the South, and costly to remove snow in the North (although it seems that most shows are filmed in the Summer).
I would also think that fallen snow is easy to shoot, but falling snow would be a production nightmare. One flake gets on the lens and you have to reshoot the whole scene.
“Third Watch” is filmed on location in NYC and has frequently featured snow. One snowy episode in particular was the one where Sully was drying out in the cabin.
How 'bout MAS*H? (which, unlike some of the above mentioned, counts as a sitcom).
The weather was usually somewhat relavent to the story, as it would be for people living in tents with very little protection from the elements. But generally it followed a reasonable sucession of seasons where sometimes it was winter and sometimes it was summer. (Of course that it followed a dozen or so such sucessions when the war lasted about two of them is another issue entirerly.)