KANSAS CITY, Mo. - It seems to happen every year. Frost forms on the windows, Christmas decorations are hauled down out of the attic, and the Kansas City Chiefs become virtually unconquerable at home.

To be sure, the Chiefs enjoy an advantage in noisy and perpetually sold-out Arrowhead Stadium at any time of year, come rain or come shine, in stifling heat or benumbing cold.

But they’re almost unbeatable in December.

Since 1995, the Chiefs are 18-1 at home in the year’s final month. They’re currently on a 16-0 December home streak, an especially comforting stat with Denver coming to town for a key showdown in the AFC playoff picture.

A 4:15 p.m. EST kickoff against the Broncos on Sunday will mark the beginning of a make-or-break five-game stretch for Kansas City against five winning teams. Three are at home against AFC opponents they’re fighting for a postseason berth.

But why the Chiefs become so all-powerful at home when Santa Claus starts showing up in the malls is a mystery even to them.

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“The fans still come out in droves here, whereas they might not in other stadiums,” said defensive end Eric Hicks. “It’s still just as loud as it was in September. It gets cold here. We usually are able to run the ball and play some pretty good defense in the month of December.”

The Broncos (9-2) are coming off an overtime victory at another tough place to win. Beating Dallas on Thanksgiving Day did more than allow them to maintain a two-game lead over San Diego and Kansas City (7-4) in the AFC West, however. Playing on Thursday also gave them three extra days to rest and recuperate.

Running back Tatum Bell, who missed the Dallas game, returned to practice at midweek and hoped to be ready for the Chiefs.

But Kansas City in December has been especially inhospitable over the years to the Broncos: between Dec. 1 and Dec. 31, they’re 1-14 in the Chiefs’ home stadium.

“Obviously, the crowd plays a part in it,” said Denver quarterback Jake Plummer. “They’re 16-0 in December, but I’m sure their home record is a lot better win-wise. We know it’s a challenge.

“Just because their record is 16-0 in December doesn’t mean the game’s over and they’ve won.”

Their hopes of catching up with unbeaten Indianapolis for home-field advantage throughout the AFC playoffs are fading. But with Plummer enjoying his greatest season, the Broncos have reeled off four wins in a row and bring the conference’s second-best record into town.

After throwing 20 interceptions a year ago, Plummer has thrown only four in his first 11 games, hitting for 2,236 yards and 14 touchdowns on a 61.5 completion percentage.