-40 is -40 on both temp scales. And I hope we never see it here or anywhere. In 1979, while active duty, I got shipped out from 92 degrees to -15 in a single day. Frozen parts never thaw sometimes. To this day I hate cold. Never like the Middle East either with temps in the 110s to low 120s. Always wondered why President Jimmy Carter hated me so much sending me everywhere I did not want to go.