May in Tri-Cities averages a daily high of 24.8°C with nights around 8°C. Expect roughly 7 wet days totalling 18mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Tri-Cities is April–May.
Based on PASCO TRI CITIES AIRPORT, WA US (6.6km), 1995–2024. 27 years of May data.