In reply to Si dH:
First of all don't take too much notice of weather forecasts, you might get an incredible downpour or spectacular thunderstorm, and it will pass within an hour or so. I remember watching a fantastic storm behind Telendos that never even hit Kaly. this time 2 years ago we had a couple of days on unsettled weather at the end of the trip, but had we been a bit more focused we could have climbed both days.
Secondly the rock does dry very quickly, particularly this time of year, and seepage shouldn't be a problem.
Plenty of crags offer shelter and overhanging rock - most in fact - but particularly Grande Grotte and Oddesey. However these are also the most popular most of the time anyway, so you might find yourself queuing for routes. Travel a bit further from Massouri, around Argonota or even Dodoni, and you might have the crag to yourself on an overcast day.
And if it is really bad, just spend the day drinking Mythos, watch the sun set behind Telendos and finish the evening listening to poodle rock in the Scorpion Bar, and I'll still be jealous