September in Richland averages a daily high of 26.1°C with nights around 11.2°C. Expect roughly 3.3 wet days totalling 7.1mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Richland is May–June.
Based on RICHLAND, WA US (3.3km), 1995–2024. 28 years of September data.