For heat, we add ice to the drinking water and make sure they have plenty of shade. You can put an entire frozen water bottle in larger waterers that will keep the water cool longer. You can also lay frozen water bottles out for them to lay on, give them inexpensive kitty litter trays with water to wade in, and even feed them cold watermelon to help keep them cool. I have one group that loves watermelon and another group that won't touch the stuff.