Boston will become aglow this week with tree-lighting events celebrating the start of the holiday season.

Mayor Martin J. Walsh will join Santa Claus and Rudolph for the annual Copley Square Tree Lighting on Monday from 5 to 6 p.m. The Old South Church bell will toll, music will play, and there will be a reception with cookie decorating, photos with Santa, and treats from the Fairmont Copley Plaza.

Faneuil Hall Marketplace will launch its new “Holiday Blink!’’ show on Wednesday, throwing the switch on an 85-foot fir tree wired with sparkling lights and synchronized music. Every evening through Jan. 1, the tree will light up beginning at 4:30 p.m. with shows every half-hour. For more details and events, go to www.faneuilhallmarketplace.com.

Then head to the 76th annual Tree Lighting on Boston Common on Thursday, from 6 to 8 p.m. Walsh and the Honourable Stephen McNeil, premier of Nova Scotia, will commemorate 100 years of friendship between Boston and Nova Scotia. The celebration will close with a pyrotechnic display.

This is the 46th year a tree has been donated from Nova Scotia to Boston as thanks for relief efforts following the Dec. 6, 1917, explosion of a munitions ship in Halifax Harbor.

As the nights grow longer and winter approaches, one way to chase away the chill is to watch some heart-warming theater.

“A Christmas Carol’’ is being staged in Lowell beginning Wednesday and continuing through through Dec. 24 at the Merrimack Repertory Theatre. Performances take place at the Nancy L. Donahue Theatre, 50 East Merrimack St. For ticket information, call 978-654-4678 or visit www.mrt.org.

Massasoit Theatre Company presents “It’s A Wonderful Life,’’ a stage version of the classic Frank Capra film, on Saturday at 8 p.m and Sunday at 3 p.m. For ticket information, go to www.massasoit.edu/boxoffice. Performances are at Massasoit Community College, Buckley Performing Arts Center, 1 Massasoit Blvd., Brockton. For details, see www.massasoit.edu/boxoffice.

And Reagle Music Theatre’s annual ChristmasTime production returns Saturday and lasts through Dec. 10 at the Robinson Theatre, 617 Lexington St., Waltham. Watch the Teddy Bears’ Nutcracker, Precision Dancers, Living Nativity, and other favorites. For times and ticket prices, go to www.reaglemusictheatre.com or call 781-891-5600.

Leslie Anderson can be reached at leslie.anderson@globe.com.