Whenever potential travelers to Hawaii are surveyed, their first questions are often the same: "How's the weather in Hawaii?", or specifically by month such as "How's the weather in Hawaii in March or November?" Most of the time, the answer is pretty easy. After all, Hawaii's weather is lovely almost every day of the year.
This is not to say that Hawaii weather is the same every day. Hawaii has a usually drier season during the summer months (May to October), and a rainier season which generally runs during the winter (from November until March).
Since Hawaii has a tropical climate, it is almost always raining somewhere on one of the islands, at any given time. But usually, if you wait a while, the sun will come out and often a rainbow will appear.
Unlike the mainland, the prevailing winds that affect Hawaii move from east to west. The volcanic mountains trap the moist air from the Pacific. As a result, the windward sides (east and north) are colder and wetter, while the leeward sides (west and south) are warmer and drier.
There is no better example of this than on the Big Island of Hawaii. On the leeward side, there are places which see only five or six inches of rain a year, while Hilo, on the windward side, is the wettest city in the United States, with an average of over 180 inches of rain a year.
The rain that falls upon the windward sides of the islands produces some of the most beautiful valleys, waterfalls, flowers and plant life on earth. The sun the shines upon the leeward sides is why Hawaii has many of the top-rated beaches, hotels, resorts, and spas in the world. The temperate winter waters of Hawaii provide the perfect sanctuary for the humpback whales, who return each year to frolic with their young.
The Hawaiian Islands are volcanically formed. Most of the islands have great altitude changes between their coasts and their highest points. The higher you go, the colder the temperature becomes, and the greater the changes in climate you will find. It sometimes even snows at the summit of Mauna Kea (13,792 ft.) on the Big Island of Hawaii.
When traveling from the coast of the Big Island to the summit of Mauna Kea, you pass through ten different climate zones. A visitor planning a trip to a higher altitude (such as Hawaii Volcanoes National Park, the Saddle Road or Haleakala Crater on Maui) should bring a light jacket, sweater or sweatshirt.
In most areas of Hawaii, however, the temperature ranges are much smaller. At the beaches, the average daytime high in summer is in the mid-80s, while in winter the average daytime high is still in the high 70s. The temperatures drop about ten degrees at night.
Read on for more about weather events and seasons in Hawaii.
Hurricanes and Tsunamis in Hawaii
In 1992, Hurricane Iniki made a direct hit on the island of Kauai. In 1946 and 1960, tsunamis (large tidal waves caused by distant earthquakes) devastated small areas of the Big Island of Hawaii. During the years of El Niño Hawaii is often affected in a way unlike the rest of the United States. While most of the country suffers from frequent rain, Hawaii suffers from severe drought.
Vog in Hawaii
Only in Hawaii can you experience vog. Vog is an atmospheric effect caused by emissions of the Kilauea volcano on the Big Island of Hawaii.
When sulfur dioxide gas is released, it reacts chemically with sunlight, oxygen, dust particles, and water in the air to form a mixture of sulfate aerosols, sulfuric acid, and other oxidized sulfur species. Together, this gas and aerosol mixture produce a hazy atmospheric condition known as volcanic smog or vog.
While for most residents, vog is merely an inconvenience, it can affect people with chronic diseases such as emphysema and asthma, although everyone reacts differently. Potential visitors to the Big Island who suffer from these problems should consult with their doctors before their visit.
Different Islands in Hawaii
Kauai has a tropical, stable climate year-round. Precipitation varies throughout the island, ranging from 20 inches on the leeward side of the island to about 50 inches at lower elevations along the northeastern shore. Temperatures in Lihue are warm, typically ranging between 80 F and 85 F throughout the year. The island's mountains are often cooler, sometimes dropping into the 40s F.
Oahu experiences a tropical, semi-arid climate. Summer is mostly dry and hot, with temperatures usually in the mid-80s. Sometimes temperatures can exceed 90 F, and very rarely, drop into the upper 50s. Honolulu receives an average annual rainfall of 17 inches, but that number is much higher in the city's surrounded mountains. There is an average of 278 sunny days per year.
Maui has an incredible range of different climates and weather patterns, despite its small size. Overall, Maui experiences tropical weather, with warm sunshine and high humidity. The temperatures typically range from 75 to 90 degrees year-round, but sometimes up to 20 degrees cooler in drier areas and even colder at the island's higher elevations.
The Big Island
Hawaii's Big Island boasts the states most diverse climate, containing more than ten different climate zones. Temperatures in Kona average in the 80s year-round, but at higher elevations on the island, like Mauna Kea, there's even snow. There are also extreme variations in precipitation: Kona is quite dry, while sometimes Hilo experiences upwards of 15 inches of rain—per month.
The small island of Molokai experiences excellent weather year-round—temperatures average around 75 F and rarely go lower or higher. Winter is slightly wetter, while spring, summer, and fall can be a little warmer, but are often cooled by the trade winds.
Lanai experiences a tropical savanna climate. It's mostly dry throughout the summer, but winter is surprisingly cool for Hawaii, with temperatures averaging in the high 60s. Lanai receives 33 inches of rain annually.
Summer in Hawaii
Hawaii experiences only two seasons: summer, called kau, and winter, called hooilo. During summer, the islands experience an average temperature of 85 F (29 C). This is also the start of the dry season and mostly perfect weather across the board. August and September are the hottest months in Hawaii, and in certain areas, temperatures in the 90s aren't uncommon. Even though summer is the islands' dry season, hurricanes are also more common during this period.
Winter in Hawaii
Winter runs from November through April in Hawaii. Temperatures aren't much colder than summer, averaging around 78 F (26 C). This is the rainier part of the year across most islands. While water temperatures don't drop too significantly, surf is much higher, making swimming risky. Not surprisingly, this season is popular among big-time surfers.
What to Pack for Hawaii
Given Hawaii's consistent temperatures year-round, you'll primarily want to pack lightweight, breathable clothing if you'll be at sea level. Depending on when you're visiting, you should supplement this with waterproof gear as well as activity-specific clothing, like hiking boots or a wetsuit. Regardless of when you're visiting, pack high-rated sunscreen—the UV index is exceptionally high in Hawaii, so it's quite common to get sunburned faster than you even realize.