Queens Crag

Even on a south-facing, exposed boulder at Queens Crag, I'd still advise caution for Sunday (March 22nd). The forecast shows 1.2mm rain returning that day with 88% humidity and a low of -0.3°C — that's fresh moisture on top of rock that's only had five dry days to recover from weeks of saturation (89.5mm in 28 days). A south-facing aspect and wind exposure do help, but the fine-grained sandstone at 300m will still be holding internal moisture from the prolonged winter wet, and that overnight freeze creates freeze-thaw risk on damp rock.

Saturday the 21st would be the better option if you're set on visiting — it's the driest day in the forecast window (76% humidity, 12°C, light wind). A south-facing exposed boulder would get the best of the limited March sun. But even then I'd say assess conditions carefully on arrival: check the base of the boulder is bone dry, tap the rock and listen for a dull sound indicating moisture, and back off if anything feels even slightly greasy.

Which specific boulder or problems are you looking at — that might help me give more targeted advice?

That south-facing boulder will be drying significantly faster than the main NW-facing crag — direct March sun, full wind exposure, and no drainage from above all help enormously. However, Sunday (March 22nd) gives only 4 broadly dry days after the last rain on the 16th, and the rock has absorbed 90mm over the past month. Even a well-exposed boulder needs time to shed that deep saturation. I'd say it's borderline — if you go, check the base of the boulder is bone dry, tap the rock and listen for a dull tone (indicates moisture), and back off if there's any doubt.

Monday the 23rd looks notably better with humidity dropping to 68% and decent wind — could that work for you instead?