September in Renton averages a daily high of 22°C with nights around 12°C. Expect roughly 8.6 wet days totalling 38.3mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Renton is July–August.
Based on RENTON MUNICIPAL AIRPORT, WA US (1.4km), 1995–2024. 25 years of September data.