In reply to robcaesar:
August is a good time to climb in Squamish, and the Pacific Northwest in general. The PNW is basically a temperate rainforest, and so the season is short by UK standards.
Whistler and Squamish are practically the same area. The good trad is centred around Squamish town though. Lots of alpine routes to be had around Squamish too of reasonable to very good quality.
As far as Banff goes (the Rockies), there's an amazing area called the Bugaboos which is in the Purcell Range. Big trad in an astounding apline environment, August is perfect. Apart from that, you're better off in Squamish for trad, although I haven't explored extensively yet.
More details from a post I wrote recently:
Geography is important here. The Coast Mountains in Canada and the Cascades in Washington are part of the same E/W watershed - wet side is west (temperate rain-forest), dry side is east (semi-desert). Visiting wet side crags before July / after September is risky weather wise, you could lose half your time. The east side is climbable all year round, but can get hot in summer. For my money, the best crags are on the wet side.
> Where might we climb?
Within reach of Vancouver (with minimal approach) with driving distances from there:
Squamish Area - Canadian wet side - 1 hr north. Lots of cracks, single pitch to all day. Not much below VS. 'Squamish Select', Marc Bourdon (2012).
Skaha - Canadian dry side - 4 hours east. Gneiss trad and sport, soft grades, good vibe. 'Skaha Rockclimbs', Howie Richardson (2012).
Leavenworth - Washington dry side - 4.5 hours southeast. Similar to Skaha, but better. Another hour east is Vantage, popular sport venue, never been. 'Leavenworth Rock', Viktor Kramar.
Washington Pass - Washington dry side - 4 hours southeast. Easy access alpine, not been yet.
Washington wet side has lots also within easy reach of Vancouver, mostly minor, but notably Index (4 hours southeast) is amazing, but very limited below HVS, and its Granite. Falcon Guide - 'Washington'.
Smith from Vancouver is about 7-8 hours I think. Smith is great, better for Sport than Trad, on the dry side but hotter than Skaha or Leavenworth in Summer (its in a kind of sheltered bowl). Falcon guide 'Smith Rock State Park'.