-11 here also.
A length of copper pipe (closed loop water heat system) on the north side of the house got slushed up, i.e. no heat this AM. Room temp was 67F, so it hadn't been off for very long.
I set the zone thermostat lower than room temp to avoid burning out the circulator pump that was vainly trying to cycle water through the pipes.
I pulled out my trusty ceramic heater, removed the protective covers off the pipes, and applied some serious radiant heat to the pipes. A cookie sheet helped to concentrate the heat on the pipe, not the wall.
1 hour later...voila...water circulating again, heat nice and toasty.