Rabbits that are housed outside live less than half as long as indoor rabbits, which normally live to be 8 to 12 years old, according to the House Rabbit Society. There are many excellent reasons to house a rabbit indoors but, if an outdoor hutch is necessary, be sure the bunny stays warm and dry during cold or intemperate weather.
Borrow an idea from the pioneers and heat a brick to warm the rabbit's hutch. Use a house brick and heat it in a very low-heat oven for about two hours. The clay will absorb the heat, so be careful when you remove the brick from the oven. Wrap it completely in a thin towel, like a dishtowel, or an old T-shirt. Place the wrapped, warmed brick in the hay pile in the bunny's hutch where it will radiate warmth for several hours. Use several bricks to generate even more heat. A heated brick set next to a ceramic water bowl will keep the water from freezing over.
Bunny Hot Water Bottle
Loan the bunny your hot water bottle but be sure you get it back in one piece. Curious rabbits will chew through just about anything -- a water bottle will look just like a tasty new toy in the hutch. Place the water bottle inside a plastic food storage keeper so the rabbit can't snack on it and flood his freezing cage. The bunny may nibble the keeper but won't be able to chew through it quickly.
Bunny Hutch Sandwich
Line the floor of the hutch with a thick layer of newspaper. The air trapped between the pages makes effective insulation. Or put one or two towels on the floor under the hay for extra warmth. It's easier to replace a towel than a bunny. Hang an old comforter or two over the cage to block chilly breezes. Place something heavy over the top to hold the comforter down and clip the edges together with chip bag clips or clothespins so the insulation doesn't flap in the breeze. This approach preserves some body heat and keeps out some of the bitter cold. However, don't leave rabbits closed up like this for long. Remove the comforters and change the floor insulation in the morning. To keep the bunny dry and warm in rain or snow, place a tarp or plastic sheeting over the comforters. Remember that air must flow so the bunny can breathe, and don't leave him plastic-wrapped for more than a few hours.
A lone bunny is a chilly bunny on a cold winter night. Two bunnies is twice the heat, and an outdoor rabbit needs the stimulation of company anyway. Consider bonding your rabbit with a buddy to make his world a little warmer.