What kind of year did you have last year?
Last year here we had horrible drought all summer and into fall. That is the season when lots of things are setting their buds for this year. I can really see the difference, even though we are having tons of rain now.
Lilac only bloomed about half as much as usual. Panicle dogwood which had been stressed by a huge infestation of 17 yr cicadas a few years ago, is now half dead. Weigela has a lot of dead spots. Redbud didn't bloom as much as usual. Not sure about the hydrangea yet.
The rain now doesn't do anything about the buds it didn't make last year.
But the oak tree may just have been slowed down. My oak tree last year took forever to leaf out, I was really worried about it. But it was ok. This year with all the rain, it leafed out sooner.