The Riverside Park Conservancy hosts its annual holiday tree lighting party, with live music and the opportunity to make ornaments and decorations. West Harlem Piers Park, W. 125th St. & Marginal St. Dec. 12, 4-6 p.m. If the weather is looking iffy, check out nyc.gov/parks/soh to find out if they party is on. More information at 212-408-0219.