Even up on the mountain, the wildflowers and grasses start going dormant and brown/golden in later August. Temperatures have very little affect there, it’s all sunlight. The ground cover starts to go to sleep even if it’s humid and 80F. That’s why the grooming team mows then. It’s over then for ground growth regardless of weather.
I don’t know, I find the claims that stuff is really early or really late might mean a shorter or longer foliage season but in the end, the peak occurs within a similar 7-10 day time frame annually. You won’t see much more of a difference than that.