Yeah, we had that experience, too. Planted a bunch of stuff rated for Zone 5. Check out the maps and that what it says we are. Most of it didn't survive the first winter after planting. After talking with the local nursery(and I mean local, not in town), we learned that our area is optomistically Zone 4 and occasionally Zone 3. Microclimates and all. 4 miles away, if you're on or right near Priest River, you could manage Zone 5 stuff.
Understand that all to well; I’m supposedly zone #7 here on my farm, since when does it get to 14* BELOW ZERO in zone 7!
Took me about 2 or 3 years but I learned and adapted; my tree types, vegetable types, and planting seasons.
Takes work but it is doable.