The best time to visit Kauai is during the shoulder season. When prices are at an all year low and crowds are away. Right after school starts, from early September to late October, you'll find a quiet Island with cheap accomodations. As you get closer to Thanksgiving, prices start surging. Try avoiding the Christmas holiday season when prices reach their peak. The weather in Kauai is beautiful all year long, slightly warmer and drier during the summer but everyday of the year feels like summer here, expect temperature in the 80s on average. The south of the Island, near Poipu, is typically much drier than the north but that's true all year long.