http://profootballtalk.nbcsports.com/2014/01/03/league-has-no-set-temperature-at-which-its-too-cold-to-play/related/
League has no set temperature at which it’s too cold to play
"......Making the situation more serious, the National Weather Service has issued a wind chill advisory from 6:00 p.m. CT Saturday until 6:00 p.m. CT Sunday, at which time the advisory converts to a warning: “FROST BITE ON EXPOSED SKIN COULD OCCUR WITHIN 30 MINUTES SATURDAY NIGHT AND SUNDAY… AND AS LITTLE AS 10 MINUTES SUNDAY NIGHT THROUGH TUESDAY MORNING.”
Players and officials will be exposed to those conditions for roughly 90 minutes in the first half of the game, along with another 90 minutes in the second half — even more if there’s overtime.............
For all parties involved, there are few viable options. The NFL could play the game on Saturday, when the temperature will spike to a balmy 25 during the day. That would entail possibly moving one of the Saturday playoff games to Sunday, or playing three on Saturday, with the Green Bay game perhaps landing in the currently vacant 1:00 p.m. ET time slot. Alternative, the NFL could flip the order of the games on Sunday, with 49ers-Packers kicking off (and in turn ending) well before the wind chill warning kicks in at 6:00 p.m. local time......"