May in Arecibo averages a daily high of 29.7°C with nights around 19°C. Expect roughly 15.6 wet days totalling 261mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Arecibo is December–March.
Based on ARECIBO OBSERVATORY, PR US (14.2km), 1995–2024. 28 years of May data.