April in Boulder averages a daily high of 17.1°C with nights around 1.6°C. Expect roughly 9.7 wet days totalling 78.4mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Boulder is September–October.
Based on BOULDER, CO US (2.5km), 1995–2024. 30 years of April data.