I know the OP is a week old, but we were up in the hwy 4 corridor over the weekend (8/11-8/12) so I thought i'd give a quick report...
Both mornings that we were there, smoke was surprisingly thick in the morning, from some time before sunrise to about 10-11am. Visibility was similar to a thick-ish morning fog (I'm terrible at estimating this, but I'd say maybe 1/4 mile visibility or so?) and the smell was pretty overwhelming. Interestingly, I guess the winds shift at some point (the official air quality reports seem to call this an inversion EDIT: apparently I can't post links but google "smoke outlook donnell fire" and look for the InciWeb PDF results) and things clear out almost entirely at some point between late morning and mid-afternoon. It was totally clear by noon on both Saturday and Sunday for us, and stayed that way until after midnight -- we were even able to get in some quality Perseid viewing last night.
Hope that helps!