Weather on Kauai: Climate, Seasons, and Average Monthly Temperatures

Clouds over Kauai island in Hawaii

Kauai's famously pleasant weather is just one of many reasons why the island is so popular with travelers. Great for outdoor activities such as hiking and surfing and less populated than the other major islands, Kauai is perfect for visitors who want to get away from the large crowds of Oahu and opt for a slower pace. Because of the location of the Hawaiian Islands near the equator, the state really only has two seasons: Summer lasting from May to October and winter from November to April. The biggest difference between the two?

Winter tends to have slightly cooler temperatures with more rainfall while summer temperatures are warmer. The good news is that when we say “cooler,” we mean it by Hawaii standards. Even in the winter it rarely dips below the mid 70s, and if it does, you will definitely hear about it from the locals.

Kauai’s lush, green landscape—perhaps its greatest asset—wouldn’t exist without the island’s regular rainfall. Its second highest point, Mount Waialeale, is one of the wettest spots on the planet. Not to mention, the perfect combination of rain and sun has made the 552-square-mile island famous for its daily rainbows and incredible waterfalls.

Avoiding the rain completely will be likely impossible, but if you want to increase your chances of staying dry, book a hotel on the south side of the island, such as Poipu, where it tends to be drier. Waimea is generally the driest area, however, there isn’t an abundance of accommodations available. Though it is known for a wetter climate, staying on the north shore of Kauai certainly has its perks too. If you’re not bothered by rain then the verdant scenery and country-feel of spots such as Princeville and Hanalei in the north will be well worth it.

Unusual weather patterns are not uncommon in Hawaii, even more so on this island. Keep in mind that Kauai is small enough to drive around in a single day, it only takes about an hour to reach almost any part of the island, and daylight hours don’t change much throughout the year. Even though it's a small island, just because it is raining on one side of the island doesn’t necessarily mean it is raining on the other. Kauai needs that constant rainfall in order to keep its green rainforests thriving.

Fast Climate Facts:

  • Hottest Month: August (85 degrees F)
    Coldest Month: January (65 degrees F)
  • Wettest Month: December (5.2 inches)
  • Best Months for Swimming: August and September (82 degrees F surface water temperature)
  • Windiest Month: July (15 mph)

Hurricane Season

Hurricane season runs from early June to the end of November each year, and some years have more storms than others. The last big hurricane to hit Kauai was in 1992 when Category 4 storm Hurricane Iniki caused over $3 million worth of damage and knocked out power for weeks on the island. Be sure to stay updated with local weather reports when traveling to any Hawaiian island during hurricane season.

Flooding

Flooding can be an unfortunate result of heavy rain and thunderstorms, recently demonstrated by the 2018 Kauai flash floods, which devastated the popular town of Hanalei and forced closures of the famous Na Pali Coast State Park. On April 13 of 2018, the north shore of Kauai saw nearly 50 inches of rain within a 24-hour period, a new national record at the time, according to the National Weather Service. Be sure to avoid driving during flash flood warnings, and sign up for weather alerts to stay prepared.

Summer on Kauai

Kauai is a bit more humid than the other popular islands of Maui and Oahu due to its rainfall. From October to March, it can be more humid in the mornings (from 77 percent to 81 percent) and go down to 65 percent to 69 percent in the afternoons. This may seem high for visitors who from a state with less humidity, but Kauai’s trade-winds provide essential relief from the muggy weather making it much more bearable. Temperatures hover in the mid-80s throughout the summer months and provide some warm nights and ideal beach weather.

For beach bums who want to work on their tans and don’t mind the summer crowds, this is the best time to visit.

What to pack: Although these months tend to be less rainy, the hurricane season may bring some temperamental weather along with it. But for the most part, hot-weather clothes like shorts, tank tops, sandals. and T-shirts will suffice. Most importantly, be sure to bring your swimsuits along, as hopping into the water to fend off the heat will be essential.

Average temperatures by month:

  • May: 81/70 degrees F
  • June: 83/73 degrees F
  • July: 84/74 degrees F
  • August: 85/75 degrees F
  • September: 85/74 degrees F
  • October: 83/73 degrees F

Winter on Kauai

As Hawaii’s rainiest island, Kauai’s winter months can bring heavy rains and slightly lower temperatures. Don’t let that deter you from visiting during the winter, however! The rain is what makes Kauai so special, and without it, you wouldn’t be able to enjoy its incredible rainforests and lush vegetation. From April to September, the average humidity in the mornings starts out around 75 percent and decreases to 65 percent in the afternoons. One of the best parts of visiting Kauai in the winter is the experience of a Hawaiian Christmas, especially for those coming from places that snow.

Lying on a sandy beach in the middle of December can be quite the novelty if you’re used to a white Christmas.

What to pack: Wardrobe doesn’t change much from summer to winter, but there can be a few exceptions. If you don’t want to purchase an umbrella after you arrive, throw one into your suitcase just in case—you’ll most likely need it at some point. Pack a light jacket as it tends to get chilly in the evenings, as well as some sturdy hiking shoes that can hold up to mud if you plan to hike.

Average temperatures by month:

  • November: 81/71 degrees F
  • December: 79/68 degrees F
  • January: 78/65 degrees F
  • February: 78/66 degrees F
  • March: 78/67 degrees F
  • April: 79/69 degrees F

Average Monthly Temperature, Rainfall and Daylight Hours

  • January: 78/65 degrees F; 3.75 inches; 10:49 hours
  • February: 78/66 degrees F; 3.29 inches; 11:11 hours
  • March: 78/67 degrees F; 4.61 inches; 11:43 hours
  • April: 79/69 degrees F; 2.25 inches; 12:22 hours
  • May: 81/70 degrees F; 2.07 inches; 12:58 hours
  • June: 83/73 degrees F; 1.61 inches; 13:23 hours
  • July: 84/74 degrees F; 1.87 inches; 13:27 hours
  • August: 85/75 degrees F; 2.13 inches; 13:07 hours
  • September: 85/74 degrees F; 2.12 inches; 12:33 hours
  • October: 83/73 degrees F; 3.82 inches; 11:56 hours
  • November: 81/71 degrees F; 4.46 inches; 11:19 hours
  • December: 79/68 degrees F; 5.20 inches; 10:54 hours
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