Do cats sweat? If not, how do they stay cool in this hot weather?
-- Curious of North Park
Ugh. Summer. Under our recent extreme conditions, Grandma and the elves have taken to stripping down to skin and spritzing each other with water. Grandma won't shed her apron, which at least keeps things a little more bearable. All in all, though, it's not a pretty sight. But it's a good example of what the science guys would call behavioral thermoregulation. When it gets hot, we seek shade, take a cold shower, sit in front of the AC-- do something to take the edge off. All animals take some sort of cooling action to regulate body heat.
As for kitty specifically, she sweats mainly through her paw pads and a little bit around her nose. Sweat glands in heavily furred skin would be more dangerous than useful, since skin-sweating like us human beans do depends on evaporation for its cooling effect. Soggy kitty would eventually expire. If things get really bad, you might see your cat pant to shed heat, though cats also pant from stress and fear, so it's hard to tell what's going on. Paw-pad sweat glands are common in the world of fur. Lack of skin sweat glands also conserves water, a real plus on a scorching day. This also explains why we carry around water bottles and cats don't.
Dogs also sweat through their feet. (You might even see a dog's or cat's sweaty footprints on a rugless floor on a hot day.) But their principal heat-shedding system goes straight to the heart of the matter. All thermoregulation is aimed at reducing animals' core body temperature. We feel the cooling on our skin, but the radiated heat has been pulled via a heat exchange system out of our internal organs. When dogs pant, they're exhaling heat more directly from their guts, a very efficient method.
One common behavioral technique for furry animals in hot weather is to flop belly-down on a cold surface. Belly fur is normally not as thick as back or limb fur, which increases the odds of radiating some body heat into the cool floor, dirt, whatever.
Only primates and horses have what we think of as skin sweat glands. So if you're fond of the old expression "sweating like a pig," in fact you're not sweating at all. In spite of the fact that they're nearly hairless, pigs depend entirely on behavioral thermoregulation. Pigs need shade, cool surfaces, air circulation, and mud or they'll end up as premature bacon.