(CNN) -- American football players and fans alike braved bone-chilling conditions in Green Bay Sunday during one of the coldest games in National Football League (NFL) history.
The temperature at the Green Bay Packers' Lambeau Field in Wisconsin was measured at four degrees Fahrenheit, with wind chill causing the mercury to dip as low as minus 14 during the visit of the San Francisco 49ers.
An arctic front pushing through the Midwest, which has become known as a "polar vortex," was the reason for the frigid conditions, with players donning long sleeves and balaclavas beneath their helmets in a bid to keep warm during the seventh coldest game the league has ever seen.
One player who persisted with short sleeves was 49ers quarterback Colin Kaepernick, who masterminded his team's 23-20 victory.
Jim Harbaugh, coach of the San Francisco 49ers, was so concerned by the cold that he had asked Kaepernick, a Wisconsin native and childhood Packers fan, three times to wear more weather appropriate gear.
"I'm a little hardheaded at times," Kaepernick, who also played without gloves, told reporters. "I played in cold-weather games before. I feel it's more mental than anything."
Lambeau Field is something of an ice fortress when it comes to the NFL's chilliest contests.
The Packers' 1967 meeting with the Dallas Cowboys, dubbed the "Ice Bowl" was played despite the temperature dropping as low as minus 14 -- with the wind making it feel like minus 48 -- securing its title as the coldest game in NFL history.