Kitties that are outside all the time, are fine, as long as they have food, which the digestion, is what helps keep them warm, same principal for horses, and they have shelter, out of the wind and wet, same with horses, as mother nature grows them a fur coat. My barn cats were fine, they were fed extra in the winter, and had the hay, they could borrow into. I even put blankies in the hay for them, the kitties, not the horsies, they had waterproof winter blankets, in at night, out during the day, with a run in shelter, unless it was very cold or very windy and cold.
During the day, when I am at work, I turn the heat down, like around 50-55, same at night. This is what they are used to, they have blankies to sleep on, which kinda have nooks and crannies, per say, like little scoops, cause the blankies are pulled over the bears. Some even burrow in the bears, and one will go under the blankies. If its like zero out, then I turn the heat up to 60. When I am home at night, I turn it up to 70, for a few hours.
This is what they are used to, and they are fine, none acts like they are cold. Being MC's they have a pretty long and thick coat, as MC's were designed, per say, to survive the harsh winters.
Many years ago, we had an ice storm, power was out for a week, no heat, no water, no power, for a whole week, and no where to go. I did have a gas stove, and turned it on periodicly, during the day, off at night. It got down to prob 40's. Even tho there was a little heat, per say, in the kitchen, they didn't hang out there, and they were all fine.
You could get a bed, that is in the shape of an igloo, have seen them at petsmart, and put a blanket in there, if your concerned. Even tho they are house kitties, most will adapt to their surroundings. You could also get one of those sweaters, like they put on little doggies, that have to go outside. Mine would wear them, they wear their halloween costumes, but they prefer sleeping on the blankies.