Show Details 21stAnnual Longmont Jazz Festival July 20, 2019 !!!! Funk Knuf Plays at 7:30 pm This year the Longmont Jazz Festival will be held on July 20th 2019 on 5th Avenue in the heart of thriving downtown Longmont. The acts will be listed soon, but make sure to put our FREE and FAMILY FRIENDLY Festival on your calendar. Bring the whole family downtown and celebrate Jazz while enjoying the Longmont Downtown Creative District.