Well, it needs to be monitored. The color changes remind me of late frost damage but this is not the time for that.

While it could be lack of enough chlorophyll production due to very cloudy skies for very long periods of time (you said it has been raining a lot), it would be normal but not cause leaves to die off.

it might also be root issues if the plant has been sitting on wet/soggy soil for very long periods of time. To see if you have soggy soil, insert a couple of fingers into the soil to a depth of 4-6" in order to get 1/4 to 1/2" of soil; press on the soil and see if it forms water droplets.

Be on the look out for bacterial leaf spot around this time too (promoted by warm, wet conditions in late spring and early summer). It usually starts at the bottom of the leaves.

Just monitor it for now.

You should be fine pruning off those leaves if you want and throwing them in the trash, not on a compost pile. Clean and disinfect the pruners when done (use either disinfectants such as Lysol, Isopropyl 70% alcohol... or a bleach solution per label directions as it may be corrosive to some tools. Remove some of the weeds near the oakleaf hydrangea.

I wouldn't be concerned at all.......just some early color change that can be stimulated by stress (too much sun, heat, drought, etc.). I seriously doubt there is any sort of fungal issue going on. Mine do this from time to time as well and they are perfectly healthy. No fungus, no bugs, no root rot.

Thank you both for your responses!

Luis; those aren't weeds. It's purple aster branches I pulled down to give hydrangea more sun and air flow. I leave all greenery in the beds as part of mulch unless it's diseased. I don't have to check the soil. It's super drenched with all the heavy rains we've had for past week or so. Tomorrow supposed to be last day of rain for awhile. Thank goodness! The new growth looks fine. I suppose I'll remove those leaves and see how they fair.

Thank you again!

Cool. Sounds like a plan.