I had one building almost freeze during this cold spell, and one freeze solid.
Got a cold alert warning from my honeywell first alert app. Building had reaches 55*, so headed the hour drive to check on it. Unit was calling for heat, but the boiler wasnt kicking in. Probably an air bubble or something stalling flow rate. Dunno. Shut down and started back up.
Two days later my milkhouse heater decided to not work, the thermostat is sometimes weird at lower temps. I forgot, and set it at 50. Well it didnt kick in. This houses my pressure tank, a washer and tankless water heater. Thought i was going to be out thousands. Only had to replace a whole house water filter and one copper 90 that burst. Turns out gas tankless have a freeze protection, so it was turning itself on. Also the washer had pumped empty, so no frozen lines there.