Polar Vortex - the answer is Miata
 

https://cimg1.ibsrv.net/gimg/www.mia...85fcec13c6.jpg
I've driven in colder with this car but it's been many years.

Celsius? I guess it doesn't really matter at that point. I know Joe said he left the NB running when it was -28f or something in Chicago.
My NB fired up at about -10. Didn't get to try it any colder. It didn't seem any less happy at those temps vs. 28f.

Celsius, yes at those cold temps they start to blend. There is more vibration in the drivetrain and everything stiffens up, doors start to get sticky from thickened grease. Everyone's exhaust looks fluffy white like a coolant leak. I could only reach about 80c coolant on the highway cruising.