slipstream is climbable in june (some years). these pics from asteroid alley- june 2- don't have to jet to new zeland.
my comment was there is usually more ice early in the season in the rockies, since the climbs don't form from melt freeze, but from water sources pouring out of the rock. yes, there is a few climbs forming later on (like see your neighbors), but most of them- if they don't form by mid november, they don't form at all.
field dont come in till december though...
i mean you can line up with 20 others to do R&D on Halloween but why bother when its probably sunny and warm in Squamish then.