The padded insulated covers made for the vehicles that I am directly familiar with, namely the M37, M211, M135, & M35, etc, helped out. I have used the for extended periods down into the -60'sF* .That in conjunction with a good heat source, such as the Arctic grade fuel heater & its overwhelming heat supply. Usually if your vehicle is reasonably tight, you have to adjust the temperature by rolling the window down. But by far, the most important covering article though, is the grill cover. I also remember coming back fro Anchorage to here (350 miles), where the fuel heater failed & temps were pushing -40F*. The grill cover is for the vehicle & it did as it should - ran like a top. The driver made out OK too, just not as comfortable.