The National Football League (NFL) was hit by the cold that pummeled the United States on Saturday as fans bundled up to watch late-season showdowns in punishing conditions.

Cities from Pennsylvania to Georgia were expected to experience their coldest-ever Christmas Eve as an arctic blast gripped much the United States, roiling travel plans during the busy holiday season.

The Tennessee Titans postponed their home game against the Houston Texans for an hour, citing "extreme weather and power outages" in the region.

"We are exploring every possibility to minimse non-essential power around the stadium," the team said on Twitter. "At all times, the operation of the game remained secondary to the well-being of our community."

The Cleveland Browns relaxed rules for fans, allowing them to bring additional items to the final home game of the regular season against the New Orleans Saints including thermoses, blankets and approved batteries for power-heated apparel.

It proved to be the Browns' coldest regular-season home game since 1981, the team said on Saturday, with the temperature at a teeth-chattering-14.4 Celsius at kickoff. The Saints iced them out in the second half to secure a 17-10 win.

For some, however, the numbing cold was little deterrent.

A handful of players for the Seattle Seahawks showed up shirt-less for warm-up exercises at Arrowhead Stadium, where temperatures hovered around -11.1C for their showdown against the Kansas City Chiefs.

Seattle melted under quarterback Patrick Mahomes' red-hot offence, however, and the Chiefs won 24-10.

For three-time Pro Bowl cornerback Marlon Humphrey, a balaclava ski mask and trousers were sufficient for warm-ups in sub-zero Baltimore, Maryland, where his Ravens booked a spot in the playoffs with a confident 17-9 win over the Atlanta Falcons. (Reuters)