Kauaʻi's temperature barely changes all year, so what really shifts month to month is rain and surf. This page walks through the year so you know what to expect, and it covers the big catch most visitors miss: the North Shore and South Shore can have completely different weather on the same day.
Kauaʻi's weather is local, not island-wide. The North Shore around Hanalei and Princeville is lush and green because it gets a lot more rain year round, while the South Shore around Poipu and the east side around Lihuʻe stay drier and sunnier. On a showery winter day you can often drive 30 to 45 minutes from a rained-out north coast to a sunny south coast. So when a forecast says rain, ask: rain where? Plan to chase the dry side rather than write off the day.
These are the wettest, coolest months, though cool here means daytime highs still around the upper 70s F. December and January are the rainiest of the year, and the North Shore gets the brunt of it. This is also peak surf season on the north and west shores and the heart of whale-watching season. Great time to visit if you want green landscapes, waterfalls running full, and whales offshore. Just keep your beach plans flexible and lean on the South Shore when the north is wet.
Rain tapers off as spring goes on. March can still be wet, but by late April and May the island is drying out, the big winter swells are easing, and the ocean is settling down across more shores. May in particular is one of the nicest months: warm, increasingly dry, calmer water, and crowds still light before the summer rush. A strong window for snorkeling and boat tours as Nā Pali season ramps up, though spring swells can still arrive, so check that day's conditions before getting in.
These are the driest months, with June and July often the driest of the year. Expect warm highs in the mid-80s F, the warmest water of the year approaching 80 F, and the calmer conditions of the year for North Shore swimming and snorkeling, though calmer is never a guarantee of safe, so still check today's conditions and posted signs. This is prime time for Nā Pali Coast boat tours and South Shore beach days, though the South Shore can pick up summer swell (see our surf season page). Summer is also the busiest and priciest stretch, so book ahead.
Early fall is a favorite of locals and repeat visitors. September and early October stay warm and dry with the warmest water of the year, the summer crowds thin out, and prices ease. Rain starts creeping back in late October and builds through November as the island transitions toward its winter pattern, and north and west swells begin returning. A great shoulder window if you want summer-like conditions with fewer people.
The Central Pacific hurricane season officially runs June 1 through November 30, with activity peaking in late summer and early fall. In practice, a storm directly hitting Kauaʻi is rare, and most summer and fall trips see nothing but normal trade-wind weather. Still, if you travel in those months, glance at the forecast in the days before you go.