How long do you think it would take a wet t-shirt to freeze solid in negative 20-degree weather? A t-shirt company in Dubuque, Iowa tried it, and it only took ONE MINUTE.
According to the YouTube video, it was negative FIFTY with the wind chill. Unfortunately they didn't have someone sexy actually WEAR the shirt. (Search for "T-Shirt Freezes in 1 Minute." It looks to be completely frozen by around :55.)