Cats like to be warm
Normal body temperature for a cat is slightly warmer than a human. Most cats also prefer a room temperature higher than most humans would enjoy. We tend to be more comfortable in the 70 degree range, but cats prefer temperatures in the 80s or even low 90s.
Many cats love curling up in a ray of sunshine. They also like snug beds or boxes, because this helps them keep their temperature up.
However, cats can get heat stroke. It doesn't happen as often with cats as with dogs, but it happens. They're not able to sweat like a human does, and rely on panting to cool themselves off. If the temperature rises, panting becomes less efficient.
Make sure your cat has access to fresh water and provide options. That is, if kitty feels cold, he or she might love curling up in a plush bed or even under a blanket. If you see your cat seek out a shady spot on the cool tile floor, he or she is probably warm. If your cat sleeps with a paw covering the nose, it might be cold and trying to warm itself.
Never leave your cat in a car, even if you have the windows cracked. On a 71 F day, the temperature in a car can rise to 116 F in less than an hour. On a cloudy 93 F day, the car can heat up to 120 F in just 15 minutes.
Young, elderly, and sick cats are more likely to become dehydrated or fall ill as a result of heat exposure.