May in Harlingen averages a daily high of 32.4°C with nights around 22.1°C. Expect roughly 4.7 wet days totalling 58.3mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Harlingen is November–March.
Based on HARLINGEN, TX US (2.7km), 1995–2024. 25 years of May data.