The town will hold its 42d annual holiday tree lighting Saturday on the town common. Organized by the Recreation Department and sponsored by Cambridge Savings Bank, the evening starts at 4 p.m. with a performance by carolers, and people attending are encouraged to participate. The tree lighting will take place at about 4:35 p.m. All the trees on the common and adjacent Simond’s Park will be lit, as will the decorative lights on Town Hall and other municipal buildings. Santa Claus and Frosty the Snowman will arrive on an antique fire engine to greet children. Santa will pose for pictures and he and his elves will distribute candy canes. Santa will be back to spread more cheer on Sunday when the Recreation Department holds its annual breakfast with Santa Claus from 9-11 a.m. at the Hilton Garden Inn, 5 Wheeler Road. Tickets are $15 and must be purchased in advance at the Recreation Department. The department has also arranged a direct telephone line to the North Pole for children to speak with Santa. The phone line, 781-270-1629, will be available on Dec. 13 from 6-7:30 p.m. only.