Sunday could mark the coldest Bears home game ever.

Pernell McPhee still won’t wear long sleeves.

“As a D-lineman, as a front-seven guy, as a guy who plays defense, I think it’s a sign of weakness,” he said.

The outside linebacker told his fellow defenders as much — that it’s a long-held Bears tradition to go bare-armed in cold weather, no matter what. Sunday qualifies as just that: with the high expected to be 3 degrees, the Packers rivalry game will rival the coldest Bears home games ever.

The Bears’ Dec. 22, 2008 contest was the coldest, at 2 degrees. The wind chill low, of -15, happened Dec. 18, 1983. Both games were against the Packers.

The Bears prepared for the chill Thursday, stretching inside the Walter Payton Center — albeit with the doors flung open — and then spending the last 75 minutes of practice outside in single-digit temperatures.

Rookie center Cody Whitehair was ashamed to admit that, when the team got to the outdoor field, he finally put on a long-sleeved undershirt.

“At the end of the day if it keeps me warm and healthy for the game day,” he said. “Then, hopefully, I can not wear sleeves on game day.”

Whitehair has never worn long sleeves in a game, but also has never played in temperatures as low as are predicted for Sunday. He and other Bears players still plan to abide by an ultra-masculine, if admittedly moronic, code.

“I’ve told them the macho stuff’s all great,” coach John Fox said. “But there comes a point where people might question your intelligence.”Guard Josh Sitton, who played eight years in Green Bay, will go bare-armed — but he tapes his forearms and wears elbow sleeves. His advice for players uncomfortable in the cold: “Tell them to grow up.”

Defensive end Akiem Hicks will meet McPhee halfway, cutting his long sleeves above the elbow.

“I’m trying to hold that Chicago tradition down,” he said.

Quarterback Matt Barkley won’t.

“I’m not a polar bear,” he said.

The Bears teased Barkley about his Newport Beach, Calif., hometown Thursday, but offensive coordinator Dowell Loggains said he did a “nice job” given the circumstances. The Bears will enter Sunday with a typical game plan, Loggains said, and adjust based on game-day condition changes.

The Bears practiced outside to test the proper cleat length and clothing. If the wind is as light Sunday as it was Thursday, Fox said, neither team should have much trouble.

“I think it’s just a race to the heaters when you come off the field,” Fox said.

Fox reminds his players to hydrate, even in the cold, to prevent cramping. Packers coach Mike McCarthy said his team was lucky to have the same conditions at home.

“We’re blessed, I guess, that we can practice in the same weather the next couple days to prepare for it,” he said.

The Bears play with heated benches and space heaters on the sideline, and remind players often to not leave their helmets in front of them — or risk them melting.

Players also smear Vaseline on their skin to block the wind, and use insulating lotion.

New Bears tight end MyCole Pruitt took all those precautions when he started in the third-coldest NFL game on record, an NFC divisional playoff in January.

The Vikings’ gjallarhorn shattered in the -6 degree weather.

“It felt like the wind just had a bunch of small icicles in it,” Pruitt, who the Bears claimed from the Vikings this week, said. “And it’s just hitting you in the face every time you try to run a route.”

Sleeves can’t stop that.

“I’m at war, I’m at combat,” McPhee said. “I ain’t got time to think about sleeves.”

Coldest home games in Bears history

Dec. 22, 2008 vs. Packers: 2 degrees, -13 wind chill

Dec. 18, 1983 vs. Packers: 3 degrees, -15 wind chill

Jan. 10, 1988 vs. Redskins: 4 degrees, -12 wind chill

Coldest games in NFL history

Dec. 31, 1967: Cowboys at Packers, NFC title game, -13, -48 wind chill

Jan. 10, 1982: Chargers at Bengals, AFC title game, -9, -59 wind chill

Jan. 10, 2016: Seahawks at Vikings, NFC divisional playoff, -6, -25 wind chill