After all the debating going on in other threads here lately I thought I might as well contribute differently and post some suitable images for this one here:
I bought the Pentax 645Z in autumn 2014 and used it a lot since in challenging weather.
My confidence in its weather sealing (with the new lenses) grew when I was able to use it in extremely wet conditions the following winter.
It got dripping wet with snow but always kept working flawlessly.
In the summer of 2015 I visited the Olympic NP, in particular also to photograph the rain forest.
I had decided to work with minimal gear and only took my ALPA TC with two lenses on that trip, and the IQ180.
It was extremely humid but ideal light for my purposes. The very wet conditions (including constant drizzle) certainly made me worry about the copal shutters, not so much about the rest of my equipment as it had never failed so far.
I tried to keep the equipment covered with a plastic bag as much as possible and kept cleaning the lens and shutter from all the water drops with a cloth. During the three days of shooting there I got away with plenty of images to my taste. Every evening I also made sure all the equipment dried completely and it worked just fine throughout the whole trip.
Last February, on a photographic trip to the Lofoten islands (Norway) I had envisioned images of braking waves and the snow covered surrounding mountains.
As I had built up so much confidence in my Pentax 645Z, I went right into the waves with it and the weather sealed 28-45mm (wearing waterproof boots and clothing myself): Salt water usually is considered the ultimate death for our gear.
But all the many waves and spraying salt water, completely (!) covering the camera and lens, didn't do any harm to it. Back at the car I would just rinse everything with drinking water....
Obviously I never removed the lens until later in the evening, when everything had completely dried.
The optically stabilized lens certainly helped to obtain sharp images hand held.
Conclusion: Using my equipment with some care and precaution, I'm able to work in pretty extreme conditions and still absolutely rely on it.
The limiting factor might rather be my own resistance to certain conditions....