Things that are good for fitness about hot weather:
Swimming. Cool water, no sweaty feeling, intense cardio, and, if you stay in long enough, green hair.
Hydration. It’s easier to remember to keep drinking water all day when it is hot.
Lighter eating. Hello, nice cold fruit, crunchy salad, sushi! Breakfast smoothie with ice, anyone?
Shade. The gym is inside in the shade and sometimes even air conditioned.
We’re already sweaty. So we might as well have something to show for it.
Go do it! Just don’t make the post-workout ice cream too big.