I find it far more difficult keeping small fur covered creatures cool than keeping them warm in winter.
They don't regulate their temperatures well. They still like to have hay and a hiding space.
Wood seems to absorb heat ,
Make sure they aren't getting full sun blasting into their living space.
And there's the ever present risk of flies, flystrike, blardy slugs, and the neighbourhood cats and foxes like to be out and about more.
Small caged pets - make sure they're not near full sun through a window.
Freeze some bottles of water, ready to wrap in newspaper. They can have a 'cold water bottle' to sit near.
Pop an ice -cube in their water bowl to keep it cooler without chilling the animals.
Slices of cucumber, watermelon,juicy peppers, selected salad leaves (I give them a cold rinse to try and sneak some fluid into them)
Keep an eye on their pee production too.
And (as the mum of a red-eyed agouti and a red-eyed Himalayan, just bear in mind that the albinos and red-eyed are more sun sensitive)
They can take advantage of some long lardy grazing days, but the heat can make them grumpy, just like people. 
If your animals are set up for summer, make sure your friends and family pets are too.