September in Hillsboro averages a daily high of 24.5°C with nights around 8.8°C. Expect roughly 7.4 wet days totalling 34.2mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Hillsboro is June–September.
Based on PORTLAND HILLSBORO AIRPORT, OR US (3.8km), 1995–2024. 27 years of September data.