“How often would you need to protect the camera from rain?”
Not super often, but it happens. last weekend was another wet weekend. Great atmosphere, but makes me very worried about the camera.
Certainly snow is quite common, as is spray from waves or waterfalls, all of which are precisely the situations you would like to take pictures of.
The OM-D eM5 II page on Olympus website has an video of backcountry powder skiing that is pretty nice.
You are correct that condensation is still an issue, even in truly waterproof cameras, which none of these one are.
Yes, lenses need to be sealed too, luckily Olympus offers quite a few models, both Pro series and a compact super zoom. If you are getting a weather sealed Panasonic body you should think long and hard though, since they only offer a few sealed lenses.