I've noticed this too. Our temps have gone from -30 in the winter to + 30 in the summer. The rate of climb I'm getting from the poor little R model 172 is horrible at the moment.
We are at 250ft above Sea level but already I've seen density altitudes of 1800ft
I'd just about got my forced approaches nailed but now I feel like I'm back to square one with the altered glide characteristics in the hot air, with all the thermals and updrafts to contend with
I'm off to spend an entire flight this afternoon trying to nail those forced approaches. At the moment they are pretty much all that is keeping me from my flight test.