If I remember correctly, my colleague Lance Bosart, who has been a Professor of Atmospheric Sciences at the University at Albany for 50 years (see this American Scientist article), considers -40ºC the "creme-de-la-creme" of cold at at 850 mb.
The NAM forecast valid 1800 UTC 29 January (10 AM CST Tuesday) has a small patch of sub -40 850 mb air over northwest Minnesota.
No point in specifying F or C since -40 is the magic temperature at which the two scales converge (i.e., -40ºF = -40ºC).
Glad to be watching it from half a world away. For Utahn's, be grateful you are on the western side of the continental divide.