The Hawaiian Islands’ Beloved Trade Winds
Spending time in Hawai‘i, you’ll often hear references to the “Trade Winds” made by local people, music, or in reading. The Trade Winds is a term for the northeastern winds that are prevalent in Hawai‘i throughout most of the year, especially in the summer months. These winds generally blow between 10 and 20 miles per hour and dictate more of Hawai‘i’s climate and lifestyle than you might think. Tradewinds blow anywhere from 70-80% of the time in Hawai‘i or about 250-300 days a year.
How the Trade Winds Form
The Trade Winds are the result of a low-pressure system that is created in the Doldroms, the region 10 degrees North of the equator, or about 10-12 degrees south of Hawai‘i.
As the sun blasts this portion of the earth’s surface, freshly heated air rises and creates a low-pressure area that is filled in with cooler air from the north. This would create a North wind, but the Coriolis effect, the rotation of the earth, causes the wind to blow northeast in Hawai‘i.
Northeastern Tradewinds of about 15 miles per hour (Green) blow across Hawai‘i in July and create calm Leeward areas (Blue) on the southwestern sides of the islands. Windy.com
The Trade Winds’ Effect on Climate
Anyone who has spent time in Hawai‘i has heard the terms “Windward side” and “Leeward side”. The windward side refers to the areas of the island that face the Tradewinds, while the leeward side is protected from the Tradewinds by each island’s tall central mountain range. For most of the year while the Tradewinds blow, consistent rain showers will hit the North and East side of the islands, creating lush tropical rain forests and beautiful rivers. During this time, the South and West sides of the islands will have clear skies, dry weather, and calm ocean. For about 25% of the year in the Winter, the Tradewinds will back down and the weather in the islands can be very unpredictable. These can be the clearest and most beautiful days of the entire year, or they can see rain and lightning storms from the south. Volcanic smog from the Volcanoes on Hawai‘i island, known as “Vog”, can linger in the islands without the tradewinds to blow it away.
The Tradewinds’ Effect on Lifestyle in Hawai’i
For residents and visitors in the Aloha State, life is heavily influenced by the weather. Everyone wants to enjoy the beautiful tropical landscape. Surfers know which breaks will have good wind conditions while the Tradewinds blow, while divers and boaters will often flee the Leeward southwestern direction. Hikers and beachgoers know to expect scattered rains on the east sides of the islands during the Summer and dry heat to the west.
Some of the best activities in Hawai‘i are found on the calm leeward sides of the islands. Whether it’s touring Kauai’s epic Na Pali Coast, snorkeling Molokini in Mau‘i, or diving outside Kona in Hawai‘I island.
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