Already mentioned this in another similar thread. We live in NPC, about 15 miles east of Lewiston. Moved here a little over 2 years ago. I'd heard all about how bad the mill stinks. I think that's way overblown. Yes, it can smell badly. But it's only relatively near the mill and it's maybe a day or two a week, if that. The odor is pretty localized. The first 6 months I lived in an RV park in Clarkston right at the confluence. Rarely smelled the mill. I wouldn't let that discourage you.
Yes, it is hot in the valley. On the other hand, when people in Moscow are shoveling 8" of snow off their driveways, people in the valley are saying, "'what snow?" Decent shopping, low unemployment, plenty of jobs depending on your skills. I shoot at the Lewis Clark Wildlife Club just because it's close. I haven't found the best places on public land to shoot just yet.