July in Waterloo averages a daily high of 29.1°C with nights around 17.2°C. Expect roughly 8.4 wet days totalling 100.5mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Waterloo is August–September.
Based on WATERLOO MUNICIPAL AIRPORT, IA US (8.4km), 1995–2024. 30 years of July data.