As you travel around the Big Island, you will soon discover that the Hawaii climate is rather unique. No place on earth has as much complex climatic diversity in such a small area as the Big Island. With 10 different climate zones, conditions vary dramatically from one part of the island to another. You will find everything from tropical rainforest to arid desert, temperate zones to a polar tundra environment, and everything in between.
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The Hawaii climate consists of essentially two seasons: winter and summer. Winter months (November through April) are warm, with daytime highs usually getting up close to 80°F (27°C), and lows in the low to mid-60’s F (17-20°C). The coolest months are January and February.
Summer months (May through October) are warmer, typically about 4-8 degrees warmer than winter. The hottest months are July, August and September when daytime highs average in the low-80’s F (high-20’s C) island-wide. Despite receiving considerably less sunshine on average, temperatures on the east side of the island tend to be only a few degrees cooler than the sunny west coast.
Much of the western and extreme southern parts of the island are arid or semi-arid. Kona on the west coast receives an average of 2” of rainfall during its wettest month. Contrast that with the 7” of average rainfall during the driest month in Hilo. Hence the waterfalls and tropical rainforest on the east side of the island!
The most significant temperature drops come with gains in elevation. Temperatures on the summits of Mauna Kea and Mauna Loa can dip below freezing at night during the winter, with winter daytime highs around 40°F (4°C). Summer daytime temperatures can soar to nearly 60°F (15°C) at the summit of these volcanoes.
Occasionally winter cold fronts will bring blizzards to the upper elevations of Mauna Kea and Mauna Loa. Icing can occur near the summit and at times the snow level extends below 9,000 feet (2740 meters).
Across much of the Big Island, the temperate Hawaii climate is complemented by the delightfully mild weather, with gentle trade winds and sunny skies most of the year. Trade winds blow from a northeasterly direction toward the equator. Consequently the north and east facing side of the island is the windward side. There is more rain making it lush and cool. The leeward side faces west and south. Because there is more sun and less rain, most of the best beaches are found on the leeward side of the island.
Trade winds account for the majority of all wind across the islands. While they may feel refreshing on land, trades can cause problems for mariners, especially as they funnel through the channels between the islands at speeds faster than over the open ocean.
Strong winds are rare in Hawaii. High pressure systems in the North Pacific can bring stronger wind gusts for short periods of time. Conversely, unusually low pressure within close proximity and northwest of the islands causes the wind pattern to change and blow from the southwest. Known as Kona winds, these winds don’t generally last long but can be quite strong. Be particularly aware of dangerous surf conditions during periods of high winds.
Hurricane season in Hawaii runs June through November, although hurricanes and tropical storms are infrequent. Even thunderstorms on the Big Island are rare. In fact, the weather in Hawaii is pretty close to perfect.
Wherever you travel on the Big Island, be prepared for lots of sun. Even on days when the sun is obscured by clouds, the UV rays are still going to find you. And due to our proximity to the equator, the effect is more intense. Cover up! Wear plenty of sunscreen, a hat, and light clothing, preferably something that has SPF protection built in. Should you happen to get sunburned, the most soothing remedy is fresh aloe, cut directly from the local plant and applied to the burn.
Again due to how close Hawaii is to the equator, the length of a day varies little throughout the year. The longest day of the year is about 13.5 hours long, and the shortest day is about 11 hours long.
Finally, if you are accustomed to swimming in the Pacific Ocean along the west coast of the United States, you are in for a refreshing treat. Our Hawaii climate means warmer, wonderfully pleasant ocean temperatures. Depending on the time of year, it fluctuates between 75°F and 82°F (24°-28°C).