Cavaillon is best visited between May and October, when the Monday market is at full strength and the Luberon landscape is in its prime. The melon season runs from late June through September — this is when the town is most itself, the stalls piled high and the air carrying the sweet smell of ripe fruit.
July and August bring Provence's peak tourist season; Cavaillon itself is quieter than Gordes or Roussillon, but the roads and nearby villages are busy. September is the best compromise: still warm, less crowded, the harvest producing exceptional melons. Winter is mild by northern European standards but many restaurants and attractions keep reduced hours.