Montpellier has the Mediterranean's reliable script: hot dry summers, mild damp winters, and over 300 days of sunshine a year. The shoulder seasons — April to June and September to early October — are the sweet spot. The Écusson terraces are warm enough to sit out, the beaches are usable, and the city isn't yet packed with summer tourists.
Summer (July and August) can hit 35°C and the old town gets crowded, but the cultural calendar is at its peak — the Festival de Radio France et Montpellier brings classical music to the city in July, and Montpellier Danse is one of Europe's biggest contemporary-dance festivals in June and July. Winters are mild — usually 10–13°C in the day — and almost everything stays open. The tramontane wind can be strong and cold in winter; pack a windproof layer.