Off season in Yellowstone often comes with localized rain or snow showers. In this case, it was flurrying lightly as I wandered the upper terrace boardwalk at Mammoth. If you look carefully, you can see a few snow flakes falling in the sky. This flurry came and went in about 10 minutes.
5D3, 24-105@28 mm, f/16, 1/160s, iso 100, tripod (and clean cotton cloth for drying).