This would be awfully early for the Sierra to be skeeter free. I would still bring DEET along until at least September.
About the earliest I remember not coming back with a slew of bites is about August 1st.
Ditto. I don't recall any bugs of consequence in August, but the last two Julys Outpost Camp was ridiculous-crazy with skeeters, black flies and no-see-ums. I suppose the low snow year will produce fewer pests, but I'm surprised there were no noticeable mosquitos in mid-June.
Last year in mid-July, half the folks I saw camping at Outpost were wearing facial mosquito netting. Big snow year though, so there was water everywhere.