July in Thornton averages a daily high of 33.1°C with nights around 15°C. Expect roughly 7.7 wet days totalling 47.9mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Thornton is September–October.
Based on NORTHGLENN, CO US (4.9km), 1995–2024. 30 years of July data.