Normally i would agree with you bigtime ... as in when i first moved to AK. Last five years snow hasn't fallen on the roads i ride till well into September. Two years ago for an end of season day trip i road the haul road to Yukon river 150 mi north of Fairbanks on Oct 2 ! But you are right given history of continental alaska ... i also remember 4 inches of snow in mid August ( it all melted however). Couple years ago i had to walk out of a float hunt trip in the Brooks Range in end of Septamber cause the river froze solid ... but that's another story ...
Given the changing weather patterns i can plan on day trips well into Sepetember. I wouldn't plan a long ride to the Beaufort Sea after Sept 10 ... cause s__t can happen! Although i would consider it if we had a pickup truck and haul trailer that followed us with bulky cloths, bunny boots and "on call" hot drinks. It would make a great picture ... in fact now that i think about it ... i know couple crazy riders i could talk into it ...
I definitely need to talk a ride soon !