I did it July 20-24. What smoke there was (to the west at the start, mainly) was confined to lower elevations and really did not affect the experience much at all...however
: it really is impossible to generalize and make predictions about this kind of thing weeks in advance. Smoke transport is governed by weather and wind patterns. If you want an idea, monitor the latest BlueSky CA/NV 2 km model run
as you get closer to your trip.