Thanks, everyone who commented on the weather post. I'm glad people like it! I had another idea that's related to something Roger said in his comment.
If the weather gets worse (or better,) which feature improves? Roger suggests rolling twice for temperature and percipitation; I would just roll once and assume both categories worsen or improve. But if I wanted to break it down, there's basically four weather elements we could track: cloud cover, wind, temperature, and precipitation. Cloud cover is less important, because we can usually just assume it's 100% in winter or if it's rained or hailing/just stopped.
If the weather changes, roll 3d6 and read them left to right, but basically only look for 1s; these indicate a weather component that doesn't change, in the order wind/temp/prec. So, a 1xx means the wind strengthens or calms down, an xx1 means the precipitation changes. All 1s means something else -- the weak sister, cloud cover -- changes. Now, we can have the wind pick up to gale-force without a cloud in the sky, or have fog roll in, or have warm rains or sudden chills.
Alternatively, you can look for 1s and 6s. Any 6 indicates something truly freaky, like tornadoes or acid rain. Not sure what "freaky temperature" would be; extremely localized temperature changes, maybe? An icicle forms on your nose in the middle of summer?