As a former Wilderness Ranger in the Sierras, and a person who staffed Forest Service Visitor Centers in the Sierras, I must add one report.
We were always amazed how many people came back to complain that we didn't tell him how bad the mosquitoes were. We'd have to put up big signs saying "Warning! Lots of mosquitoes!" And still people would come back and complain that you didn't tell us that it would be THAT bad.
Snow levels are lower than normal this year and the most voracious mosquitoes are tied to snow melt. It won't be as severe as normal, but usually that's more severe than people who haven't experienced bad mosquitoes can tolerate in the month of June. To avoid mosquitoes go before June or after July.
I have a Sierra trip planning on beginning about July 20th. I will still have lots of mosquitoes, and probably smoke.
By the way, I have been on the road living outside since May 20th. I have traveled through Eastern Arizona Western New Mexico and now Northern New Mexico. I haven't seen one mosquito. I will do a 4-day backpacking trip very soon in the Pecos wilderness and I won't have to bring any bug spray with me. Imagine that.