I'm feeding a stray cat (and possum) on the back porch. The cat has been sleeping every night on a porch wicker settee with a flowered cotton cushion. I tried to enhance the warmth and comfort of the settee by placing a kitty cave covered with an old jacket at one side and a wool sweater at the other side. I also have Mysty's old cardboard box enclosed in some plastic, including a cotton pillow stuffed inside with an old woolen blanket on the porch, but the cat went inside the box only a few times and since the possum ventured inside, the cat has been avoiding the warmer cardboard box! I hope this shelter is sufficient for the winter. The black and white cat is quite large and doesn't fit into the kitty cave.
If the cat continues to stay on the porch, I'm thinking of buying a wooden house/shed like structure (mini-barn) that I can place on the porch and fill with straw. I can also keep the cat in the garage on cold, winter nights, or install a cat door on our shed. The porch is covered, but the winter elements can be very severe, and unfortunately, the porch faces northwest, exposed to the strong, wintery, blizzard-like winds.