During the 2018 Superb Owl I was ice fishing on Red Lake in Minnesota and we lost heat overnight, because it got cold enough the propane for the heater wouldn't boil in the tank. I woke up when I noticed my nosehairs frosting up, and it was already -23C (-10 degrees freedomheit) in the fishing shack. I went out to swap LP tanks, but the one on the regulator was still mostly full, so I disconnected it, fed the LP line back through the bulkhead into the fish house, and hooked it back up inside, but the LP tank was still so cold that it took 10 minutes for the fuel to warm up enough to provide enough pressure to the heater for me to light the pilot light. It was -32C (-25F) inside the fish house by the time I was able to get the heater working, by that that point I'd gone out and started the truck because it was getting dangerous to life in the fish house and I wasn't sure I was going to be able to get the heater to work before my brother and I were going to have to evacuate for the night.
We caught a shitload of walleyes, it was great.
It didn't get up to -40 at the landing until 11 AM that day according to the resort that keeps the roads plowed on the lake.