How long does it take to get frostbitten?

Varies by temp. Frostbite occurs more quickly at lower temperatures. So if temp is just around 32 degrees, it could take hours. If temp is below zero, could occur as quickly as 5-10 minutes on exposed skin. Also, injured skin (dry chapped cheeks) is susceptible more quickly. And with things like dry ice, frostbite can occur almost instantaneously - so be careful!