We typically don't hunt during rain "storms", as the visibility tends to be really poor due to fog in the hills and mountains where we hunt (Unit 20 for many years now). And, if you don't have a stove for your tent, once you are wet on a remote hunt, you may be wet for the duration of the hunt...I keep hearing about the importance of a glassing tarp. I'll be after caribou for the first time and I'm curious, are caribou really active during rain storms or are guys just trying to maximize their limited time on a fly in hunt?
But, there are quite a few days in remote AK where it's not raining HARD, but enough to get you good and wet over time if you don't have a tarp or something to sit under. And, there are often days where a strong or persistent wind can make it really cold to sit and glass - a tarp is great for a windblock on those days.
We typically cut 8'x8' Tyvek sheets, soak them in the clothes washer for a few hours, and then run them through a wash cycle without any detergent. Makes them soft and quiet....then each guy carries one in his pack, can be used as the makeshift shelter from wind and rain, and then used to put the quarters and other meat on if you shoot a bou.