The best time to visit Saint-Tropez is May to June or September to early October, when the Mediterranean is warm enough to swim, the beaches are open, and the town is lively without the suffocating crowds and prices of peak summer.
May–June: The shoulder season sweet spot. Temperatures reach 22–26°C, the sea is warming up (18–21°C), and Pampelonne's beach clubs are in full swing. Hotel rates are meaningfully lower than July–August, and you can actually get a restaurant table without a reservation made weeks in advance.
July–August: High season. The town fills to capacity — traffic into the peninsula can back up for hours, parking is almost impossible, and prices for everything roughly double. That said, this is when Saint-Tropez is most electric: the quay is pure spectacle, the beach clubs are in full swing, and the nightlife at Les Caves du Roy and similar venues is legendary. Come if you want the full experience, but book everything months ahead.
September–October: Often the best kept secret on the Riviera. Crowds thin noticeably after the first week of September, the sea is at its warmest (24–25°C in September), and the light turns golden and painterly — exactly as Signac saw it. Many restaurants and clubs stay open until mid-October.
November–April: Most beach clubs and many restaurants close. The town is very quiet — charming in a different way, but not for those seeking the full Saint-Tropez experience. The Annonciade Museum stays open year-round.