reporter: in emergency rooms across the midwest, frostbite the top concern. with these temperatures, it can set in in just five minutes. is not safe for anyone to be outside for any period of time. reporter: frostbite victims, like this man in chicago, wait too long for help. it wasn t just his hands and feet. he ended up with pneumonia as well. reporter: escaping could be a matter of life and death. alex perez, abc news, milwaukee. great work being done there. meanwhile, thousands of passengers are still stranded as airlines struggle to catch up with the weather-related backlog. jetblue is the most extreme example with the carrier suspending service at four major airports. all flights are expected to resume by 3:00 this afternoon. nearly 10,000 flights have been canceled from saturday through monday. amtrakle is warning passengers that service will be suspended between washington and d.c. and new york city and albany. and things are not much better for drivers. gio ben