I think this article (in Norwegian; the title translates to "How water resistant is your camera?") is relevant regarding weather proofing in general, primarily because the site is run by one of the largest camera stores in Norway:
We regularly have cameras with water damage coming in for repair. The manufacturer will claim that it's not covered by the warranty because it's water damage, while the customer will claim that it's a warranty issue since the camera was supposed to be weather resistant. Then you're stuck, unless you're willing to bring the case to a small-claims court.
Since the camera manufacturers won't specify the degree of resistance, it's hard to pin the blame for the damage on faulty weather proofing.
In practice, they think the professional models (Nikon D4, Canon 1D X, and the like) are well protected, along with a few models from Olympus (E-3, E-5, E-30 and OM-D E-M5; there's no mention of Pentax).
For other cameras, they think that no matter what the manufacturer claims regarding weather resistance, you should be very careful with the camera in damp conditions, e.g. inside a tent on a rainy day. So ignore the claimed weather resistance and use a rain cover or plastic bag to protect the camera anyway.
They do think the weather resistance is fairly effective against dust. (Although keep in mind that this is from the perspective of Norway: We have plenty of rain but very little dust.)
But there are no guarantees in either case - "less resistant than I was led to believe" is not accepted as a warranty issue.