It depends...
I don't know what current conditions might be. I can tell you about a dozen years ago in June, my wife and I did a north-south traverse, staying at Mad Hut and Lakes. The first two days were absolutely gorgeous -- clear skies, cool, good breeze, and no bugs whatsoever.
However, on the third day, as we headed down from Lakes to the top of Tuckerman Ravine, the black flies all hatched at once -- an entire generation spilled out of whatever special region of Hell is reserved for them. We dosed up liberally with Cutter's DEET on every exposed surface, and things seemed OK, as long as you didn't draw breath too sharply. The operative phrase here is "Seemed...", as, unbeknowst to me, the little buggers were working their way through the gaps in my ragg wool socks and the cotton liners I used to wear, and gnawing on the 3" or so of un-DEETed leg underneath.
I ended up at Urgent care the next day with legs blown up like a rhino... the doctor, who found this endlessly funny, counted 63 distinct bite marks.
So yes, black flies can be a problem on the high Presis, if your timing is just right.
