I MUST BE FREAKIN INSANE TO BELIEVE THAT THIS IS ANYTHING BUT NORMAL...
Yes, you are.
This is a phenomena called a Cold Front.
Show me ANYWHERE in the world where such drastic temperature swings are common.
This "cold front" hit so hard.. so fast.. that it knocked out the newest and weakest link/ "state of the art" bridge.
http://www.cbc.ca/news/canada/thunder-bay/nipigon-river-bridge-closed-transcanada-1.3397831
Sudbury began to rumble at approximately the same time.
http://www.cbc.ca/news/canada/sudbury/sudbury-earthquakes-jan10-1.3398208
maybe you better stay away from saskatchewan where 30 degree temperature swings are very common.
By the way, you certainly can use statistical variance to determine significant variation from climatic norms. All the records are available to do this, at least in the USA I know. You can just use the last 30 years, that should be fine.