It my first hot summer since i started my reef tank, its quite a small tank, 100L, and have seen the temp peak at 28.1C. Lows through the same period have been 25.7C. It appears to be coping and parameters have stayed within norms.
Hermit crabs seam a bit more active and I have a couple of serif snails that havnt moved for a while and may not have made it but fish and corals seem tobe fine.
What are you seeing in you tanks?