Not very well tbh. Three quarters of the year we have wet, coldish weather which the rabbits like and so do I tbh. Compared to a heatwave which makes me dizzy and brings on a headache. The rabbits, lie down and pant, and hide from the sun. I have found the best things are cool surfaces to lie on, icy things to lie beside, fans and lots of cool fresh water to drink and shade. We had a sunny day yesterday which was too much for all of the us. The bunnies did not even run around outside, they just lay down and soaked up the rays for a bit and then went to get some shade and dig earth scrapes.