A stronger, darker, spiced beer that often has a rich body and warming finish suggesting a good accompaniment for the cold winter season.
Overall balance is the key to presenting a well-made Christmas beer. The special ingredients should complement the base beer and not overwhelm it. The brewer should recognize that some combinations of base beer styles and special ingredients work well together while others do not make for harmonious combinations. THE ENTRANT MAY DECLARE AN UNDERLYING BEER STYLE AS WELL AS THE SPECIAL INGREDIENTS USED. THE BASE STYLE, SPICES OR OTHER INGREDIENTS NEED NOT BE IDENTIFIED. THE BEER MUST INCLUDE SPICES AND MAY INCLUDE OTHER FERMENTABLES (SUGARS, HONEY, MAPLE SYRUP, MOLASSES, TREACLE, ETC.) OR FRUIT. If the base beer is a classic style, the original style should come through in aroma and flavor. Whenever spices, herbs or additional fermentables are declared, each should be noticeable and distinctive in its own way (although not necessarily individually identifiable; balanced with the other ingredients is still critical). English-style Winter Warmers (some of which may be labeled Christmas Ales) are generally not spiced, and should be entered as Old Ales. Belgian-style Christmas ales should be entered as Belgian Specialty Ales (16E).
Anchor Our Special Ale, Harpoon Winter Warmer, Weyerbacher Winter Ale, Nils Oscar Julöl, Goose Island Christmas Ale, North Coast Wintertime Ale, Great Lakes Christmas Ale, Lakefront Holiday Spice Lager Beer, Samuel Adams Winter Lager, Troegs The Mad Elf, Jamtlands Julöl
You can view the complete style details on the BJCP website. The 2008 style guide is obsolete but there is a similar 2015 style that you can view below...