RTB....your situation is actually very common..happens alot here in "Winterpeg" Manitoba as well....last I heard...our winters might actually be even worse than Saskatchewan( I know our football is definitely worse)!!!!!
Problem is that the manufacturers don't glue the flooring down, except for the outer edge, and some don't even do that...so in the sub zero temps, it contracts...some people have told me that when they replaced the flooring they glued it all down, and never had another problem...others have just replaced with laminate, problem there is extra weight and that changes all your heights for everything in the trailer.
Rick