University of Minnesota spokesman Garry Bowman said the tarp and heating system were put in place Saturday to protect the field. More than 1,500 workers have moved 40,000 cubic yards of snow from the stadium over four days to get it ready for the Vikings, who need to play at the school after the Metrodome's roof collapsed last week.
The Bears practiced at Northwestern University's outdoor artificial-surface field in an attempt to simulate the playing conditions at TCF Bank Stadium.
"You (media) guys are talking a lot more about that than our guys," Bears coach Lovie Smith told the Chicago Tribune on Saturday. "If you ask them those questions (about field conditions) -- like 99 of 100 people would answer your questions about it ... that's not an issue with us. We possibly have a chance to win our division. ... We play outside (at Soldier Field), so it's not an issue for us.
"They (Vikings) play inside, we normally play outside. We feel like this is an advantage for us," Smith added.
Williams Arena will be open across the street for fans to keep warm before queuing up for the first-come, first-served seating. Free coffee and hand-warmers also will be distributed.
The Associated Press contributed to this report.