One of the biggest worries people have when planning their trip to the tropics is the weather. Will it rain? Is it going to be too hot? What about hurricanes?
Let’s deal with the last one first. There have been only three recorded hurricanes in Hawai‘i in the past 200 years. One in the 1950s, one in the ’80s and ‘Iniki on Sept. 11, 1992, clobbering Kaua‘i. None have hit O‘ahu, so you should probably spend your precious worry energy elsewhere.
As for rain, it works like this: The prevailing winds (called trade winds) come from the northeast, bringing their moisture with them. As the air hits the Ko‘olau mountains, it rises, cools and condenses into clouds and rain. So the mountains and shoreline facing the northeast, called the windward side, get the lion’s share of the rain. Look at the rain graphic, and it will make more sense. Often by mid-morning, the rising, cooling air causes clouds to form in the mountains, giving them an exotic, mystical look.
Once the air has had its moisture wrung out, it sinks and warms on the southwest side (called the leeward side) and often has minimal rain potential. So areas like Waikiki get little rain. The exception is when we get winds from the south or southwest—called Kona winds—where the rain pattern is reversed. These Kona winds only happen about 5–10 percent of the time, most often in the winter.
Waikiki has an embarrassingly equable climate for Oahu weather. The average high is 84 °F, and it has never gotten above 95 °F since thermometers have been in the islands. Waikiki gets only 20 inches of rain per year, and when it does rain, it’s often in the form of short, intense showers.
Average humidity ranges from 65–75 percent. And ocean temperatures go from 75 °F in February to about 80 °F in September.
Bring and drink lots of water when you are out and about, especially when you are hiking. Dehydration sneaks up on people in this Oahu weather. By the time you are thirsty, you’re already dehydrated. It’s a good idea to take an insulated water jug with you in the car or one of those 1.5 liter bottles of water. Oahu weather is almost certainly different than what you left behind, and you will probably find yourself thirstier than usual. Just fill it before you leave in the morning and suck ’em up (as we say here) all day.
Learn about Hawaii weather and get real-time Oahu weather updates in our Hawaii Revealed app. Every island has a Weather chapter that has everything you need to know about Hawaii Weather and forecast.
Here are the links to download the app on your device.