Le Havre has a temperate maritime climate — mild, damp, and frequently overcast. Rain falls throughout the year without a pronounced dry season. Summer (June–August) brings the best weather: temperatures of 18–22°C, longer days, and the best conditions for the beach at Sainte-Adresse. The city is never crushed with tourists even in summer, and queues at the museums are rarely a problem.
Spring and early autumn are good alternatives: the light on the chalk cliffs and the Seine estuary is often excellent in April–May and September–October, and hotel rates are lower. Winter is grey and often windy, but the museums are warm and the city feels more like itself without any visitors at all.
The main local event worth timing around is Le Havre Triathlon in June and the Nuit des Musées in May, when the MuMa and other museums open free of charge for an evening. The city also holds a maritime heritage festival every few years that fills the harbour with historic vessels.