Kauai is pleasant year-round, but April-June and September-October offer the best balance of good weather, lower rates, and thinner crowds, avoiding both the wet winter swells and the busy summer school-holiday season. Winter (November-March) brings the best chance of seeing migrating humpback whales and the biggest surf on the North Shore, but also the highest rainfall and rougher seas that can cancel Na Pali boat tours. Summer is driest and calmest for water activities but comes with the highest prices and fullest beaches, especially on the South Shore.