Weather in Oahu: Climate, Seasons, and Average Monthly Temperature

The weather on Oahu doesn’t change much throughout the year, and the island really only has two seasons (winter and summer). In general, Oahu is usually much drier on the west side of the island (the leeward side) than the east side (the windward side), so you will find most of the greener landscape along the coastal areas to the east. As one of the two states in the U.S. that doesn’t observe daylight savings time, Hawaii doesn’t experience a substantial variation in daylight hours, either. Throughout the year there is only about an hour discrepancy in sunrise and sunset times on the island of Oahu.

One of the things the makes Oahu so special is its trade winds. For a majority of the year, winds coming from east to west on the island provide a welcome and necessary relief from the hot, humid environment. Laying your towel down at the beach may be a bit more difficult during these windy times, but you’ll definitely appreciate it once the hot sun starts beating down.

From mid-November to February, waves on the north shore of Oahu can get up to 30-40 feet in size. That doesn’t mean you still can’t enjoy the beach for some lounging and barbecuing, just leave the surfing to the pros.

Hurricanes

Hurricane season typically runs from June and November when the water surrounding the island warms, but keep in mind that temperamental weather can occur at any time of the year. A hurricane making landfall on Oahu is rare, but it is best to be prepared with an emergency plan even if you are just visiting. It also may be a good idea to invest in travel insurance if you’re traveling within this period, as poor weather often leads to canceled flights, tours, and activities.

Flooding

Oahu isn’t Hawaii’s wettest island (that title goes to Kauai), but flash flooding is still possible, especially during the rainiest months between October and February. Check for weather alerts during your stay and don’t drive during heavy rainfall.

Vog

While Oahu doesn’t have active volcanoes anymore, the island can still be affected during heavy lava flow on Hawaii’s Big Island about 200 miles away. Air pollution from active volcanoes (“vog”) can affect those with breathing problems.

Popular Areas of Oahu

These two areas are the most visited due to their consistently good weather.

Waikiki

It is easy to see why Waikiki quickly became the tourist mecca during the early years of Hawaii’s transition into a major vacation spot. The southern shore sees the best weather year-round by far, with much less rain and almost-constant sunshine. The resort area in Waikiki is famous for gentle waves, making it the perfect spot to learn how to surf, paddleboard, or kayak. If you’re visiting this area during the busy tourist seasons coinciding with school breaks—between December to March and again from June to August—be prepared for large crowds.

North Shore

On the other side of Oahu, the north shore towns of Haleiwa and Kahuku experience mostly pleasant weather throughout the year, with an added appeal to those wanting to escape from the busy Waikiki area. The north shore beaches at Sunset Beach, Pipeline and Waimea are where tourists and locals go to witness some of the best waves in the world. In the winter months the waves reach epic heights, but in the summer months the water will be calm and great for swimming.

Summer in Oahu

The early Hawaiians named this time of year “kau,” the warm season. During this time the sun is almost always directly overhead on Oahu and the weather is warm and dry. July, August, and September often see the highest temperatures on Oahu, and the rain is more sparse. Depending on your tolerance to heat, this may make it the best or worst time to visit the island. The Oahu sun is even more relentless during the summer, so sun protection is a must. (Remember that the state of Hawaii banned sunscreens with ingredients that are harmful to reefs, so there’s a chance yours might be confiscated at the airport if it isn’t reef safe.) In August, the sun will rise around 6 a.m. and set at 7 p.m. The water is also warmest in the summer, making it the optimal time for swimming in the ocean, though the water temperature rarely drops below the low '70s even in the coldest months.

What to Pack: Since this will be the warmest time of the year, jackets or coats aren’t necessary. Opt for shorts and T-shirts or tank tops during the day, and bring a light sweater for going out in the evenings (though you probably won’t need it). If you plan on going to the beach then a bathing suit with a cover-up will suffice, and a pair of sandals. 

Winter in Oahu

The cooler season, named “ho'olio” by the early Hawaiians, describes the time when the sun is low on the southern side with a greater abundance of clouds in the sky throughout the island. Generally, there will be an average of 11 daylight hours between the months of November and February, with an uptick to 13 hours between April and August. While the trade winds blow throughout the year, it is often a bit stronger in winter.

What to Pack: Packing lists won’t change too much during the winter months, but you might want to bring a sweater or sweatshirt for the evenings. Hiking will require closed-toed shoes with good traction in case of rain. The ocean conditions will be colder as well, so pack a windbreaker if you plan on going on a boat in the winter.

Big Wave Season

If you’re dreaming of jumping into the water for a swim, you’ll want to avoid the north shore during the winter months (unless you’re a professional big-wave surfer). The surf in this area completely transitions from about October to February, attracting world-renowned surfing contests at Banzai Pipeline and Sunset Beach. Starting in May the waves recede on the north shore, and remain small through around September. When the waves are big in the north, it is safe to say the surf is smaller on the south shore, and vice-versa. This means that no matter what time of year, there is surfing to be enjoyed through participation or pure spectatorship on Oahu.

Whale Season

Each year from December to May the waters off Oahu become a temporary home to humpback whales who have migrated to the warm area to breed and give birth. If you don’t want to book a whale watching tour, try a hike to higher elevations like Makapuu Lighthouse Trail or Diamond Head.