Coldest I've experienced was 8 C when I was around 8 years old and were in one of the cities on top of a mountain. I thought my toes were gonna fall off.
Coldest I've experienced was -40. I just bundled up and toughed it out for a few days. It was when I was in uni so I spent a lot of time walking around campus. I survived!
-40 is exactly the same in both Celsius and Fahrenheit so inb4 any whining.