I couldn't resist responding to this.

Did you know that -40 degrees is a special temperature? It is the exact temperature where Fahrenheit equals Celsius. -40F =-40C

That sure is one evil cold temperature! Both my father and husband's brother have special sayings for such a temperature.

My dad: "It's as cold as a witch's t*t in the Klondike." Actually, I think this is from my father's paternal grandmother. She was notorious for such sayings. Out of curiosity, I just googled this and apparently, some local New Jersey historian speculated on it at Origins of Cold as Balls and Cold as a Witch's Teet - Mr. Local History Project Everyone in my family lived in western NJ or right across the river in PA. If I had had children, they would know this, too.

B-i-l: "It's as cold as at 3 am at Kharkiv train station." Kharkiv train station is in Ukraine. Not sure of the exact origin.

Do you have any local sayings like this?

One more fact. At -44F the gas in a propane tank (such as for a gas grill) starts to cease vaporizing. They refer to that state as "boiling".