When is black fly season in northern British Columbia, Yukon Territories, and Alaska?

Answer 1

That depends on the latitude, elevation, drainage, and local climate. In general, the blackflies in that part of the world are worst in mid to late June.

It would be rare to see blackflies before June and after early September. There are places that never see blackflies such as the Kluane Ranges in Yukon and some of the rocky Aleutian Islands in Alaska.

There is only one Yukon Territory.

Answer 2

as soon as the snow leaves until it freezes again