Lensrentals analyzed the weather sealing of the A7rIII by tearing down the camera
Except for the bottom this camera has thorough and extensive weather sealing, as good as any camera I’ve seen.That being said, the bottom of the camera is not protected worth a damn. If you’re out in a sprinkle or shower, this probably doesn’t matter; water hits the top first. But if you’re in severe weather, near surf, or might set your camera down where someone might spill something, you need to be aware of that. If I knew I was heading out in such conditions, honestly I’d tape up the bottom of the camera or encase it in plastic taped all around the body. Yeah, battery changes will be a pain, but the new battery is supposed to last a lot longer.
We now know where Sony needs to improve the weather sealing. I hope the next A7s3 will have fixed this issue.