December in Harlingen averages a daily high of 22.6°C with nights around 11.2°C. Expect roughly 6.3 wet days totalling 39.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Harlingen is November–March.
Based on HARLINGEN, TX US (2.7km), 1995–2024. 25 years of December data.