Have you ever hiked for 4 hours with a pack (at least partly up hill) in pouring down rain?
Yes, quite a number of times..
Did you stay dry (10,20,30....100%?)? What were you wearing? Do you think most of the water was from the outside (rain) or inside (sweat)?
When young and dumb - sweat. I'm now old and dumb, so usually a mix. I sweat a lot when exerting, but stay a fair bit drier with proper ventilation - poncho and windshirt - no goretex.
From a strategy stand point you would:
A. Not go hiking if the forecast was 90% chance of rain.
B. Go hiking in spite of a bleak forecast because you are not .....a pantywaist.
C. Change plans to make the hike shorter.
I tend to B, because I don't have the luxury of rescheduling most of the time, and I'm confortable with my wet weather gear. Having said that I've certainly done A and C at various times.
Note that A is sometimes prudent. I bail on hikes walking down exposed mountain ridges if the forcast is that I will be doing it in thunderstorms.