I had an XSi (450D) that spent some quality time out in drizzle on a Scott Kelby photowalk a few years back. The XSi isn't the least bit weather sealed, nor was the lens, the 18-55mm kit lens that came with it. I did use a skylight filter on the front, and had to dry it with a paper towel every 10 minutes as the drizzle would accumulate on the filter and prevent the little Rebel from focussing.
https://grahamglover.zenfolio.com/p940513647
The camera continues to work fine today, albeit in the hands of my niece.
If you want a weather resistant camera, you'll need to do a bit of research work. The 5DMkIII, in conjunction with certain L lenses fitted with a filter on the front, can be weather sealed. Typically the lens will have a rubber gasket on the mount to prevent or at least resist water/dust from entering the body. That's important. The filter ensures you're also protecting your L lens investment. If you're going to be out in bad weather for any length of time, you can get and/or make plastic bags with rubber bands and/or strings that can help minimize your gear's exposure to the elements while giving you access to the controls to take pictures.
I did have occasion when I needed to shoot with my 5DMkIII in drizzle with a 24-105 F/4L and an EX580 II Speedlite. (I don't recall if I had a filter on the lens, though I did have a hood on it to minimize what was hitting the front element of the lens.) I was out there for a half hour. Everything continues to work fine today.
Good luck!