Sorry for the late reply. For some reason, when I replied before it did not appear and I did not notice it. Maybe I hit Preview instead of Post and didn't verify.
Regardless, for me, the mosquitos were not that bad south of Fairbanks but maybe that was because I was early or just lucky. When I started riding south from Prudhoe Bay, they were really bad, but slow in a few places. A couple of days for a few hours, I literally had to ride in a bug head net which still sucked because then the wind would sometimes blow the netting against the face and then the demons would try to bite. I use a Da Brim which helped immensely to keep the head net from my face. In camp, it was almost mandatory though to wear the head net as were long-sleeve & long pants with lots of Ben's Wipes in use. I didn't get bit too much (for the amount of mosquitos flying around) but it is the buzzing in the ear that drives me bat sh!t crazy while riding. Luckily up north, not much traffic which was good as I rode like I was a severely drunk idiot slapping his head while cussing out loud

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I met a ranger at the Yukon River who said there are two waves, the first are slow and big, and the second are small and fast. I found that to be true and luckily only had a little bit of the second as I was "early" into the season. The season moves just like the temp warms up as the days heat up. South early (including lower part of AK mainland), then north.
My guess is you will have either both or the 2nd wave in July. Maybe it is worth a call to someone midway through your route and ask them what wave you would be in.
Again, in early June, it really was not too bad in the south so I personally would not let that bother you.
If you have not already booked though, I would seriously consider the Jasper to Missoula (or wherever you make it to) along the Icefields Highway instead. While Alaska is nice, if I was on a shortened tour, I would do that over a tight fitting tour where the snow peaks are not as prominent, but that is just me.
Tailwinds, John