Whenever potential travelers to Hawaii are surveyed, their first questions are often the same: "How's the weather in Hawaii?" followed by questions about the specific months they intend to visit. 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 experiences only two seasons: summer, called kau, and winter, called hooilo. The drier season spans the summer months (May to October), while the rainier season lasts from November until March.
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 (13,803 feet) on the Big Island of Hawaii. In most areas of Hawaii, however, the temperature ranges are much smaller. At the beaches, the average daytime high in summer is between 80 and 90 degrees Fahrenheit (around 30 degrees Celsius), while in winter the average daytime high is still well above 70 degrees Fahrenheit (near 25 degrees Celsius).
Rain can vary dramatically throughout the islands as well, much of that due to prevailing winds. There is no better example of this than on the Big Island of Hawaii. On the leeward side, there are places which see only 5 or 6 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.
Hurricane Season in Hawaii
In September 1992, Hurricane Iniki made a direct hit on the island of Kauai, and caused extensive damage. It was a rare event, though, and the risk of a hurricane in Hawaii is fairly low, with the most likely time for problems in July, August, and September. 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.
Different Islands in Hawaii
Kauai has a tropical, stable climate year-round. Annual precipitation varies throughout the island, ranging from 20 inches on the leeward side to about 50 inches at lower elevations along the northeastern shore. Temperatures in Lihue are warm, typically ranging between 80 and 85 degrees Fahrenheit (27 and 29 degrees Celsius) throughout the year. The island's mountains are often cooler, sometimes dropping below 50 degrees Fahrenheit (10 degrees Celsius).
Oahu experiences a tropical, semi-arid climate. Summer is mostly dry and hot, with temperatures usually above 80 degrees Fahrenheit (27 degrees Celsius). Sometimes temperatures can exceed 90 degrees Fahrenheit (32 degrees Celsius), and very rarely, drop just below 60 degrees Fahrenheit (16 degrees Celsius). 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 Fahrenheit (24 to 32 degrees Celsius) 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 state's most diverse climate, containing 8 different climate zones. Temperatures in Kona average above 80 degrees Fahrenheit (27 degrees Celsius) 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 degrees Fahrenheit (24 degrees Celsius) 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 well above 60 degrees Fahrenheit (16 degrees Celsius). Lanai receives 33 inches of rain annually.
Summer in Hawaii
During summer, the islands experience an average temperature of 85 degrees Fahrenheit (29 degrees Celsius). 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 above 90 degrees Fahrenheit (32 degrees Celsius) aren't uncommon. Even though summer is the islands' dry season, hurricanes are also more common during this period.
What to pack: 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.
Winter in Hawaii
Winter runs from November through April in Hawaii. Temperatures aren't much colder than summer, averaging around 78 degrees Fahrenheit (26 degrees Celsius). 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: Hawaii's weather is pleasantly warm, so you'll mostly want to pack clothing similar to what you'd pack for any summer destination, but that can vary depending on where you're planning to visit; some areas can get downright cold. 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.
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 vog is merely an inconvenience for most residents, 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.