In reply to Red Rover:
Well yes of course you can make a judgement when you get there - if it looks or feels at all damp don't climb. But if you've driven any distance the temptation to climb can be hard to resist and it's all too easy to think 'this doesn't look that bad'.
Some bits of course are slower to dry than others - Northumberland wall dries first, whereas the start of Pit and the Pendulum needs a prolonged drought. But the bulk of the crag is not quick drying, so I'd always advise watching the weather carefully in the run up and only go if everything looks good.
Post edited at 15:25