Yes, cats and dogs, just like humans, need access to plenty of cool water on hot days. Make it colder, and more interesting at the same time, by floating ice cubes in the bowl. And adding water to the food like you're doimg is a great idea! If your cat prefers to drink from the sink, leave the faucet running at a thin trickle during the hottest part of the day.
**The following taken from a post from last year by Hissy**
Signs of heat stroke
Anxiety, possibly demonstrated by pacing
Respiratory distress or hyperventilation
(Breeds with flat noses may exhibit this earlier because of compromised airways.)
Dark red gums
Increased internal body temperature
Your cat's internal temperature should be between 100.5Â° and 101.5Â° F. A temperature of 104Â° or more is a definite warning sign.
You can help your cat survive extremely hot weather by keeping him indoors in a cool interior room. Rubbing him down with a damp towel will help; so will immersing his feet in a tub of cool water. Wrapping a cold compress under the cat's neck will also help cool him off. He may fight at first, but most likely will appreciate it once he gets used to the idea.
Strangely enough, cats affected by external heat may refuse to drink water, exacerbating the problem of dehydration, so you may want to "force" water by using an eyedropper or syringe. Be careful not to shoot the water down his throat as it can enter his lungs and/or cause choking. Just dribble a drop or two at a time in the corner of his mouth will help hydrate him and draw his interest to drinking on his own.
If your cat exhibits any of the signs above that lead you to think he is suffering heat exhaustion, cool him down as quickly as possible by immersing him in cool water, and then wrapping him with wet towels. Then get him to the veterinarian immediately. This is a serious, potentially fatal condition.