You asked

Is the canon rf 10 20mm f 4l is stm weather sealed?

Here is what the site says about that.

From Canon RF 10-20mm f/4L IS STM: Canon RF 10-20mm f/4L IS STM: A zoom lens by Canon for Full frame cameras, 10-20mm f/4. Specs - Maker: Canon - Focal length: 10-20mm (zoom) - Maximum aperture: f/4 - Made for: Full frame sensors - Mounts: Canon RF - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Canon RF): as marked, 10-20mm. - On APS-C (Canon) (Canon RF): like 16-32mm on full frame; f/4 gives about the depth of ...

From Landscape: What matters: - Resolution and dynamic range. Landscapes are often printed big and include bright skies and dark foregrounds in one frame. A sensor with a lot of dynamic range keeps detail in both. Full-frame and high-resolution bodies shine here, but any modern sensor does well at base ISO. - Weather sealing. You'll be out in wind, spray and drizzle at dawn. A sealed body and lens survive it. - A tilting ...

Quoted from this site's pages.

From these pages