Dr C can I attempt to answer your question of 'what's a three dog night'?
It seems that you tough people that live in those cold provinces of the Great White North in the winter, sometimes have to have some of your sled dogs sleeping in the entrance tunnel of your igloo. They will act as an insulated door. With only one dog in the doorway it probably is quite nice outside, maybe twenty below, but a 'three dog night' is nasty outside and you're very thankful your in an igloo.