Ever notice how your cat prefers the bonnet of your car as a place to sit after the engine has run, even in cold weather? Cats are drawn to warm surfaces. A heated outdoor cat house would be an extra special treat for your cat. You may already have an outdoor cat house for nice weather, one that is insulated against wind and elevated above the ground or cement. As long as the cat house is dry and not draughty, it will be adequate shelter. But adding a heating element will go the extra distance to keep your cat comfortable in cold weather. Low-level radiant heat is the safest solution.
Begin with a cat house you already have or construct a wooden box. Experts recommend cedar; it repels fleas and weathers well. You'll be creating a downsized doghouse, in essence, with two small doors. Often, cat houses will have a flat roof for the cat to lounge on. For multiple cats, you'll need a larger cat house. Some cat houses are multistory. You can insulate the inside walls with carpet scraps or styrene foam; do not use fibreglass.
If you will be using an electric heating pad, verify an electrical socket is within 6 feet of the cat house or ensure the connection to an outdoor-safe extension cord is protected from moisture. You may wish to connect a ground fault circuit interrupter (GFCI).
Purchase an outdoor-use electric heating pad made for outdoor cats or a non-electric thermal mat. You can find both online.
Install the pad or mat inside the cat house.
Plug in the heating pad.
Verify that outdoor use of an extension cord is permitted by your local building codes. If you're worried the cat will scratch or chew on the cord, hide the cord inside PVC pipe.
Be certain to provide water for outdoor cats, as well-heated cats can become dehydrated quickly. Never use a heating element that increases temperature beyond 38.9 degrees C, your pet's ideal body temperature.