Rethimno is a year-round destination with a genuine town life that does not entirely depend on the tourist season. July and August are hot (35°C or more), very busy, and the beaches are crowded. June and September offer excellent swimming weather with more manageable crowds. May and October are ideal for sightseeing — warm enough to swim, cool enough to walk all day, and the old town is largely reclaimed by locals.
The Rethymno Carnival in late winter (February or early March) is one of the largest in Greece, an old tradition that fills the town with costumed processions and street parties. The summer Renaissance Festival brings concerts and theatre performances in the Fortezza during August. In winter the town is quiet but fully functional, with good tavernas and a working university presence that keeps it lively.
The shoulder season (May–June and September–October) is definitively the best time for most visitors: the sea is warm, the old town is pleasant, and accommodation prices drop significantly from their August peaks.