Briggs will take part in a "Polar Plunge" into Lake Michigan with members of ESPN 1000's "Carmen, Jurko & Harry Show" to raise money for Special Olympics Illinois.
"I'm a little nervous," Briggs said on the show Thursday. "I'm going to see if I have this wet suit that I had. If so, then I'm going to try to use that. If not, then it's old school shorts and swim trunks."
The water temperature in Lake Michigan currently is in the upper 30s.
While Briggs, 31, will make headlines with his charitable gesture, he vowed to stay positive regarding his contract. He said last season that he wanted more money or he wanted a trade. He then went out and earned his seventh consecutive Pro Bowl berth.
"I hope that I retire a Bear," said Briggs, who's played all nine seasons in Chicago. "This is home. It always has been. All I can be is hopeful and stay positive.
"They brought in a new GM, and I think we have all the more reason to be positive."
Briggs wouldn't talk about the possibility of holding out if he doesn't get a new deal.
"I'm staying as positive as possible," Briggs said. "I've ruffled some feathers last year and aired out some of my feelings. Right now I just want to focus on enjoying this offseason, get in during offseason workouts and start focusing on a championship."
Bears coach Lovie Smith said earlier Thursday at the NFL combine that he hopes things are improving with Briggs' contract situation. The two talked recently at the funeral for the wife of former Bear Tommie Harris.
"I did have a chance to talk to Lance a little bit," Smith said. "Lance is family to us. Again, you're talking about a guy who's been here every day I've been here, and plays better football every year. He knows how much we like him and want him to be a Bear forever. So yes I've talked to him. Hopefully things are getting better on that front."