Jerba has a mild Mediterranean climate with hot, dry summers and mild, sometimes wet winters. The island gets around 300 days of sunshine a year, which makes it popular with northern Europeans from April through October.
The peak months of July and August are hot (35°C or more) and crowded, with the package resort strip on the northeast coast at its most intense. Spring (April–May) and autumn (September–October) are the sweet spots: warm enough to swim, cool enough to walk comfortably, and far quieter. The spring pilgrimage to El Ghriba Synagogue, usually held around May (33 days after Passover), is worth timing a visit around — it draws thousands of Jewish pilgrims from across North Africa and is a remarkable event to witness.
Winter is warm by northern standards (daytime highs of 15–18°C) and very quiet. Many resort hotels close, but Houmt Souk continues as a working town and the interior is at its most peaceful.