Nantucket's peak season runs from late June through Labor Day in early September. This is when the beaches are warm, the ferry schedule is most frequent, and every restaurant and shop is open — but also when the island is at its most expensive and crowded. Main Street in July is a different experience from Main Street in October.
The shoulder seasons offer a quieter, often better version of the island. Late May and early June bring wildflowers, fewer crowds, and mild weather; the Daffodil Festival in late April draws dedicated enthusiasts. September and October are arguably the best months: the summer crowds have thinned, the water is still warm from summer heating, the light is golden, and the cranberry bogs on the south side of the island turn brilliant red.
Nantucket in winter is genuinely quiet — some restaurants and most shops close entirely. The ferry schedule contracts and small planes are the primary link. A few hardy visitors come for the solitude and the light, but it is not a destination for most.