There are commercially-available heated cat beds which typically plug in to an electric outlet and provide a warm, cozy place for your cat to curl up. But before you buy, there are a few things to consider.
First, if you are using one of these beds outdoors, be sure that the model you are buying specifically states it is for outdoor use. Many of the heated cat beds are designed for indoor use, and are at risk of electrical malfunction if used outdoors.
Next, consider the size of your cat, and pay close attention to the dimensions of the cat bed. Some of the more popular models have high sides, but are so small that only a small to medium size cat can comfortably use the bed. Larger cats would not fit, and due to the sides being so high, they cannot simply hang over the edge. Those large cats will not even use the bed.
Lastly, consider using a cat heating pad instead of an actual bed. This gives you greater flexibility in what bedding you use. Rather than being stuck with a particular style bed, you can place the heating pads under any number of bedding types, from a simple pile of towels or blankets, to a nice basket with a pillow. This gives you the benefit of the heated cat bed without being stuck with only one or two styles that may not even match your home decor.Christy - Information about a Cat Heating Pad from http://catheatingpad.net