December in Hillsboro averages a daily high of 7.7°C with nights around 0.8°C. Expect roughly 20.1 wet days totalling 156mm. A hard month to visit for comfort alone.
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 December data.