I looked after my first piggy when I was aged 11, many, many years ago. Not knowing any better, I kept him on his own, living outside in a hutch for the first year. It didn't make a big impact on me at the time, but apparently one wintry night the temperature plummeted to minus 27 degrees C. It makes me cringe now to think how cold he must have been, but he lived to tell the tale. He was young and strong, well insulated and well fed.
I'm not proud, and certainly not advising that any pigs should be kept outside in the winter - mine now are all inside and enjoying the warmth. It must have been a miserable night for him, and not one I'd like to repeat for any piggy in my care now, but it shows how robust a piggy can be.