It really just depends on where you are hunting.
In Alaska south of the Brooks Range or on the Pac Coast I wouldn't hunt with out top quality rain gear and good wool to wear under it.
In the Rockies it tends to be a lot drier. Synthetics work ok, but aren't fire proof. Wool works great, but isn't rain proof. I have only ever had it rain once while hunting elk in my life. And that shower lasted 10 minuites.
I had similar luck in Germany in the Alps. Rained for a few minuites and then it was over.