Hi ND farm girl!
My Hydrangeas haven't appreciated the high temps we've had this summer, at all! Are yours
growing in direct sun? Last year mine sunburned because they were in the sun for half the day (& it got pretty hot then, too.) So, I moved the
plant (ended up with 5 of them) to a spot where there was full shade...
then my neighbor trimmed the hedge on the fence line between our yards, which exposed half of my Hydrangeas to full sun! The ones that were exposed to the sun ended up sunburned (blossoms AND leaves), yet the ones that remained in the shade looked almost the same way! I'm thinking that they're reacting to the heat... (or maybe we didn't keep them watered enough.
I know that Hydrangeas need LOTS of water!)
Have you looked at the Garden Helper's page on
Hydrangea cultivation requirements & tips ? There is some good information there, & a link to more of the same.