Weather on the Big Island, Explained

The east side of the Big Island gets up to 40 times the rain the Kona side does, often in the same week. Temperature barely matters: highs stay in the low 80s to low 90s all year. Rain is the real variable, and it is intensely local, driven by trade winds that blow in from the east most of the year and break on the windward slopes.

So the question is not when to come but which side to stay on. Hilo is the rainiest city in the country at 151 inches a year, yet a 30-minute drive often finds blue sky. Pick your side first; season, hurricane odds, and cloud cover are adjustments around that, not the main call.

The influence of Hawaiʻi’s location on its weather

Few places on earth sit as far from anywhere as Hawaiʻi. The nearest mainland coast is 2,285 miles away, Japan is 3,850 miles off, and Australia a full 5,673 miles. There is a lot of ocean between Hawaiʻi and everywhere else, and that ocean shapes the climate more than anything.

Because of its proximity to the equator, temperatures are mild and the length of the day is fairly constant through the year. The dominant winds come from the east and northeast (the trade winds, explained below). And because of all that ocean and the high volcanoes, rainfall can change dramatically over short distances, while severe storms stay rare.

The two Hawaiian seasons: Winter (rainy season) and Summer (dry season)

The Hawaiian Islands have two main seasons: good and better.

Just kidding. We call the two seasons summer and winter and skip spring and autumn. Summer is the dry season, winter the rainy season. The main difference between them is rainfall, with more rain falling in the winter months.

Summer and winter temperatures

Summer falls between May and October. Daytime highs at sea level run between 85 and 90°F (29 to 32°C). Hawaiian winter runs October through April, with daytime highs between a balmy 79 and 83°F (26 to 28°C). At low elevation it is rare for the temperature to climb above 90°F (32°C) or drop below 65°F (18°C).

This steady, pleasant weather is driven by the warm ocean. Surface waters around Hawaiʻi stay between 77°F (25°C) and 83°F (28°C) all year, so the air never cools off much.

The mean annual air temperature for the Island of Hawaii. Image credit: Giambelluca, T.W., X. Shuai, M.L. Barnes, R.J. Alliss, R.J. Longman, T. Miura, Q. Chen, A.G. Frazier, R.G. Mudd, L. Cuo, and A.D. Businger. 2014. Evapotranspiration of Hawai‘i. Final report submitted to the U.S. Army Corps of Engineers, Honolulu District, and the Commission on Water Resource Management, State of Hawai‘i.

Rainfall during the Hawaiian winter and summer

The wettest months on the Big Island fall between November and March, but winter rains rarely disrupt vacation plans. Weather here is intensely local, so you can usually find a sunny spot nearby when it is raining where you are.

Related: 15 rainy day activities for the Big Island (+ 2 to avoid).

So where are the wettest and driest spots on the Big Island? The windward east side around Hilo gets by far the most rain. As the map below shows, Hilo gets between 10 and 40 times as much rain as the driest parts of the island: the Waikoloa resorts, the stretch between Waimea and Kona, the summits and western slopes of Mauna Loa and Mauna Kea, and the southern tip.

The mean annual rainfall map for the Island of Hawaii. Image credit: Frazier, A. G., Giambelluca, T. W., Diaz, H. F. and Needham, H. L. (2016), Comparison of geostatistical approaches to spatially interpolate month-year rainfall for the Hawaiian Islands. Int. J. Climatol., 36(3), 1459-1470. doi: 10.1002/joc.4437

The same wet-dry pattern holds month by month. November and March are the wettest, while in the summer months rainfall can drop to half the peak rate.

Average monthly rainfall for the Big Island. This animation has been prepared using the following works: Giambelluca, T.W., X. Shuai, M.L. Barnes, R.J. Alliss, R.J. Longman, T. Miura, Q. Chen, A.G. Frazier, R.G. Mudd, L. Cuo, and A.D. Businger. 2014. Evapotranspiration of Hawai‘i. Final report submitted to the U.S. Army Corps of Engineers, Honolulu District, and the Commission on Water Resource Management, State of Hawai‘i.

You can find more maps of the rainfall patterns in the Rainfall Atlas of Hawaii.

Each island has a wet side and dry side: the trade winds

Weather patterns in Hawaiʻi are driven by the trade winds. These winds blow out of high-pressure zones in the north Pacific, pushing cool, moist air down onto the islands’ eastern and northeastern slopes. They earned the name because their steady, predictable pattern carried trade ships across the Pacific as early as the 16th century.

On the Island of Hawaiʻi, the trade winds (blue arrows) blow the vog from its main source on the volcano (white plume) to the southwest, where wind patterns send it up the island’s Kona coast. Here it becomes trapped by daytime (onshore) and nighttime (offshore) sea breezes (double-headed arrows). When light “Kona” winds (red arrows) blow, much of the vog concentrates on the eastern side of the island. Image credit: USGS

Trade winds over the Hawaiian islands blow from the east and northeast between 250 and 300 days a year (source).

Once the trade winds hit the volcanoes, the air is forced upward. As it rises the moisture condenses into clouds and rain. In weather terms, the side the wind comes from is the upwind or windward side; the far side is the downwind or leeward side.

So rain mostly falls on the elevated windward side. Coastal areas, and especially the south and west leeward sides, stay drier. You can see this clearly in the rainfall maps above, and it drives the climate zones across the island: a humid tropical climate on the windward side, arid zones on the leeward side.

Read more about the 8 climate zones on the Big Island.

Hurricane season in Hawaiʻi

A hurricane is the strongest class of tropical storm: sustained winds of at least 74 mph (64 knots), force 12 on the Beaufort scale. The same storm is called a typhoon or a cyclone in other parts of the world.

Hurricane season in Hawaiʻi runs from June through November, with most activity in August and September. The islands themselves rarely see anything worse from these storms than heavy rain and big surf.

Part of the reason is the volcanoes on the Big Island, which act as a natural buffer. Their high peaks disrupt the wind circulation and help break up, divert, and weaken a storm as it moves toward and over the island.

So what does a hurricane mean for you, the visitor?

As noted above, mostly bad weather and a lot of rain.

Depending on how close the storm is and how strong the winds are, a tropical storm or hurricane watch may be issued for the Big Island. When that happens, local shops and national parks can close for a day or a few. In the most extreme cases, flights are delayed or rescheduled.

Four simultaneous tropical cyclones heading for Hawaii on July 22, 2016. From left to right: Darby, Estelle, Eight-E (which would soon become Georgette), and Frank. By National Oceanic and Atmospheric Administration, VIIRS, captured on SNPP satellite, source, Public Domain, Link

For more on the past hurricanes that have affected the Hawaiian islands since the 1950s, see Hawaii’s Hurricane History and Hurricanes in Hawaii.

Current tropical storm info (worldwide) is at the Tropical Tidbits website.

What is the best time to visit Hawaiʻi?

There is no single best time to visit Hawaiʻi. Temperatures are good all year, so the choice comes down to crowds, rainfall, and daylight, and those pull in different directions depending on what you want.

Best time to visit: high season

The Hawaiian islands are busiest during high season, which splits into two parts:

• The first runs roughly mid-June through the end of August, when families travel over the summer holidays.
• The second falls between mid-December and mid-March, when people come to escape winter at home.

The Big Island never gets as crowded as Oʻahu in high season, but prices climb with demand.

Best time to visit: Temperature

Temperatures stay constant and pleasant through the year, but rainfall does vary. The driest months run May through October, the occasional hurricane aside.

If you are trying to escape winter on the mainland, come during the cold months back home.

Best time to visit: most daylight

One thing people rarely consider is the length of the day. Days in June are about 2.5 hours longer than those in December. If you are planning an active trip, more daylight adds real hours to your visit.

Best time to visit: for the different islands

If you already know which island(s) you want to visit, let that guide your timing. See our island-specific guides:

• The best time to visit the Big Island
• The best time to visit Maui
• The best time to visit Kauaʻi
• The best time to visit Oʻahu

Sunny skies and cloud frequency on the Big Island

While pleasant temperatures are a given on the Big Island, sunny skies are not.

Clouds are normal here, especially around Hilo and Puna. Most days on this side of the island are a mix of sun, cloud, and the occasional spatter of rain.

Other cloudy areas include the central and south Kona coast, the northern valleys including Waipiʻo, and Pahala in the south. The sunniest skies and the best beach weather sit on the Kohala coast.

You can find the average yearly cloud cover for the Big Island on the map below. A value of 1 means clouds the whole year; a value of 0 means the skies are always clear.

The mean annual cloud frequency for the Island of Hawaii. Image credit: Giambelluca, T.W., X. Shuai, M.L. Barnes, R.J. Alliss, R.J. Longman, T. Miura, Q. Chen, A.G. Frazier, R.G. Mudd, L. Cuo, and A.D. Businger. 2014. Evapotranspiration of Hawai‘i. Final report submitted to the U.S. Army Corps of Engineers, Honolulu District, and the Commission on Water Resource Management, State of Hawai‘i.

Hilo: the rainiest city in the USA

With all of that out of the way, time to address the elephant in the room: is Hilo really the rainiest city in the USA, and, if so, why on earth should you visit it?

Yes, by any reasonable measure Hilo is the rainiest city in the United States. It gets about 151 inches (3.84 meters) of rain a year, spread across roughly 295 days (NOAA).

So why should you visit?

• Outside of hurricane season it is rare to get a fully rainy day in Hilo. More often it rains for an hour and then the sun comes back.
• Rain here is also local, so if you really cannot stand it you can get in the car and drive 30 minutes to find sun.
• The rain is what gives Hilo its character: it is the reason the town is ringed by rainforest and waterfalls.

Wait, doesn’t the internet say cities in Tennessee, Florida, or Louisiana are the rainiest in the states? Look at their annual totals and they top out around 65 inches, less than half of Hilo’s. Those rankings filter on city size and list only the largest hundred or so cities, and Hilo is too small to make the cut. A few tiny Alaskan towns like Ketchikan and Whittier do get more rain, and Hawaiʻi’s own mountain summits get far more, but none of those are cities. Among US cities of any real size, Hilo wins.