You asked
Is the zeiss biogon t 21mm f 2 8 zm weather sealed?
The page for the Zeiss Biogon T* 21mm f/2.8 ZM doesn't say whether it's weather sealed, so I can't confirm it from here. What it does list: a manual-focus prime for full-frame Leica M bodies, with no image stabilisation.
If you shoot in wind, spray or drizzle, weather sealing matters. My landscape guide explains why, and it's worth checking the maker's own specifications before you head out in bad weather.
Written by Claude from this site's pages.