In reply to dinodinosaur:
Just to add to Dan’s response, a local who knows the cliffs really well also said that a northerly wind seems to dry it out. It sounds counterintuitive but Dan’s explanation makes sense.
Another tip is to check for wet streaks on the walls towards the boulder choke. Those bits are the last to dry out, so if it’s visually dry there, it’s probable fine on the more landward routes (whereas if there are wet streaks, the landward routes might still be ok but probably not primo).
Temperature is another consideration. It’s a great place to hide on a hot day but humidity is relative to temperature and warm air can hold more moisture, so 80% at 25C is going to involve more humid air than 80% at 15C. Hence grease is perhaps more likely at higher temperatures, all other factors being equal. I’m happy to be proven wrong with this theory but I did have a couple of weeks in Pembroke a few weeks ago when the headline temperature was 15-20C and there was no grease at all (albeit we didn’t go in the Leap), whereas from my experience grease is not uncommon in August when it’s warmer.
Sounds like you got what you wished for in the end!