June in Longmont averages a daily high of 28.5°C with nights around 10.5°C. Expect roughly 8.6 wet days totalling 50.9mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Longmont is September–October.
Based on LONGMONT 2 ESE, CO US (2.1km), 1995–2024. 17 years of June data.