Methinks there maybe some logic in this saying.

From what I remember oaks are temperature sensitive when it come to leafing,
whereas the ash responds to daylight length. In warmer springs the oak will
leaf before the ash and the saying then predicts a dry summer. Remembering
what I read in one of Lamb's books, he said that 70% of the time weather
patterns will 'carry over' into the next season, hence a warm summer will
follow a warm spring. Now this definitely didn't happen last year!

I gather in these climate warmed years, the oak is nearly always leafing
before the ash (it certainly wasn't always so). This is having the effect in
woodlands of shading the ash by the oaks and they are now being 'out
competed'. An ashless future may await us.
________________
Nick G
Otter Valley, Devon
83 m amsl
http://www.ottervalley.co.uk