UKC

whats the best time of year for intermediate bouldering in the peak district?

Every month is good, if the weather treats you right. 

There's three days in Spring and another three days in autumn  when it's perfect conditions. Just between 'too wet & cold' and 'too hot & midgie'. All the other 359 days aren't worth it and you should probably just head Indoors lol

For a particular crag you can look at it's stats to see popularity throughout the year. For example https://www.ukclimbing.com/logbook/crags/stanage_plantation-101/#stats. Graphs will be approximately the same for crags with the same rock type.

In general you want it to be cold and not humid and not raining recently but good days can happen any time of year in the UK.

This weekend looks spot on for the grit.

Dry for a few days prior. Cold but sunny. Low winds. 

Best conditions (when dry): winter

Most reliable conditions: Spring and Autumn

May 

...and 95% humidity

High humidity is normal when air temps are just above zero. Doesn't stop conditions being excellent in winter at times, especially if the sun is out.

Sure, but "High" in those conditions is about 60-70%, as is forecast for Monday (currently) in Hathersage. Good day to get out if you're free!

Well spotted. Flipping cold, but sunshine and relatively low humidity could make for a good day. I think I’ll save myself for then. 

March, April, September and October are usually best. For colder conditions, February can be better than the months before because there is more sunlight (stay out longer) and sometimes that means more time to dry out

I guess my point is humidity readings seem irrelevant just above freezing on sunny rock. I guess the air is heated from the rock and so the relative humidity will be a good bit lower than forecasts indicate.