Know that your outdoor cats will need a shelter inside the garage unless it is heated and there are few that I recommend
K&H makes a soft sided insulated outdoor cat house that comes with a heated pad that is covered with soft Sherpa pad. The heat element on this pad does not generate heat until your cat lies on it and then it will keep your cat warm. I own this cat house and recommend it for garage use because the product needs protection from rain, wind, ice and snow.
|Here is cat K&H cat house and it is showing wear from being outdoors on covered porch. Note it elevated off the ground to prevent rain or water runoff from penetrating. This cat house is very light weight and can be lifted by the wind.|
Now if you are on a budget but still want to provide your outdoor cat warmth in the garage then you can always get a heavy cardboard box and fill it with straw.
Here is a photo of the dish pack size box that I set on its side and started with layers of carpet on the bottom then topped that with a fleece blanket that was folded to provide additional insulation, then a foot of straw. The straw is a natural way to provide the cat with a cozy and comfortable resting area. Straw is natural insulation. I set this box cat bed under my work bench in my garage. The area was away from the door opening and excess drafts.
Here are photographs of the box and the feral cat in the box bellow.
Know that K&H also makes a self-warming bed (see my photo bellow) These beds are great for cold rooms however if your garage gets bitter cold then I recommend that you put these beds in an insulated cat house like an igloo or other cat house.
Also if your garage is not heated then it does get cold and while the cat's internal body temperature may be warm from the self-heated bed their ears and nose will be cold. It is wise to invest in an insulated cat house or make your own especially if you keep your cats outdoors or in your garage during the winter months.
Here is a video that will show you how to make an outdoor shelter for your cat.