...we're in for a splash; ash before oak, we're in for a soak.
In North Wales yesterday, the oaks were definitely predicting a drier summer than we had last year. The ashes had barely started to show their leaves. This might tie in with the Met Office predictions that this summer may be somewhat warmer and drier than the past couple of years. But then again, after two years of heavy summer rain, I could have quite a good go at predicting a drier summer too, without the need for huge levels of number crunching.
For other weather related folklore, have a look here.