August in Waterloo averages a daily high of 28°C with nights around 15.7°C. Expect roughly 8.5 wet days totalling 97.4mm. 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 August data.