I used to make these things as a kid. You pile a big mound of snow in the yard, about 5 feet high in a rough dome shape, then you jam it full of 6 inch sticks all over the outside, like a pin cusion except that you push them in all the way. Then you wait for a nice cold overnight freeze.
The next day, you pop a hole in the side and you excavate inside just up until you start hitting the ends of the 6 inch sticks you stuck all over the outside. This ensures a 6 to 8 inch snow wall. Then.. you move into it! Snow fort for adults! Woohoo!
Igloos are too hard to make, the snow's gotta be just so. A Quinzhee you can make pretty much anytime a few degrees below zero. The kids love 'em, although there's always the danger of collapse if they try and climb on the roof. We supervise closely just in case we gotta dig them out quick(hasn't happened so far), and we break them if a thaw melts the walls too thin. They sure don't last as long as an igloo!