In reply to Barri:
If it's hot,
Earl Crag is a good place to head, being high on the hill and north facing. Great climbing!
You may be disappointed with
Caley Crags, as although it's probably the best bouldering in the country when in condition, that's not in late summer. You'll probably think it's ugly (it is!) and disgusting (it's overgrown, midgy and generally revolting in summer, and the subtle, technical climbing is frankly impossible if it's humid).
Almscliff is excellent in dodgy weather. It dries in minutes and catches any breeze going, keeping the midges away (obviously, if it's still and humid you'll get savaged in the evening when the light drops, so just go to the pub). It has nice views and is generally user-friendly. A super-classic venue not to be missed.
I have a real soft-spot for
Shipley Glen, but do your research before heading there, it's not everyone's cup of tea. It isn't the most aesthetic venue, but some of the problems are really good (high, technical, tricky).