Here are some key dates to remember if you're hoping to celebrate the holiday season in Somerville.

If you've got a great event not listed here, leave a comment and email chris.orchard@patch.com.

Now (since Nov. 27): Illuminations Tour trolley tickets on sale at Blue Cloud Gallery in Ball Square. Visit www.somervilleartscouncil.org. for more information.

Nov. 29: The Next Wave and Full Circle tree lot opens in Foss Park. When you buy your tree there, you support the Next Wave and Full Circle schools, which teach Somerville students with special academic, social, emotional, and behavioral needs. The tree sale continues until Dec. 19.

Dec. 1: Winter Craft Market in Union Square, organized by Union Square Main Streets.

Dec. 1 and 2: Davis Flea Holiday Market in Union Square.

Dec. 2: "Local is for Lovers" holiday market, organized by Somerville Local First, at The Center for Arts at the Armory.

Dec. 1 and 2: Tons of markets and open studios. Basically, this whole weekend is full of markets and events. It's a good weekend to celebrate in Somerville (and convince your friends and family to visit). Union Square Main Streets has compiled this great list of all that's happening.

Dec. 6: Christmas tree and Hanukkah menorah lighting at Somerville City Hall, followed by a meet-and-greet with Santa Claus. Music will be provided by the high school band and the El Sistema music program. It starts at 5:30 p.m.

Dec. 6:  DARBI's—Davis Area Resident/Business Initiative—"Midnight Madness: An Amazing Shopping Extravaganza."

Dec. 8 and 9: Davis Flea Holiday Market in Union Square.

Dec. 15: Illuminations Tour. According to a description from the city of Somerville, "The 45-minute tours will showcase holiday light displays in our own Somerville. Tours leave from (and return to) Somerville City Hall where coffee, hot chocolate, and cookies are served. Entertainment at City Hall includes choral music, courtesy of the Somerville Community Chorus and craft activities for children." Tours begin at 4:30 p.m.