Bakken oil fields of North Dakota it was usually around ten below f. Pretty much start work predawn and don't wrap up operations till dark. That was a brutal Christmas season. Worst day was twenty below zero f. and nothing would start. Supervisor never arrived due to frostbite trying to get his vehicle to the job and another vehicle blew radiator as it had not been winterized. I was only employee who had winterized my radiator . BTW, frostbite toes was a daily hazard even with special boots. For that you take a few minutes in the warmup shack until you can feel your toes again.