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, but the speed can vary seasonally and is influenced by the Pacific High. Tradewinds blow anywhere from 70-80% of the time in Hawai‘i or about 250-300 days a year. Hawaii covers about 10,931 square miles, making it similar in size to Connecticut, and is surrounded by the open ocean, which moderates its climate and amplifies the effects of the trade winds.
How the Trade Winds Form
The Trade Winds are the result of a low-pressure system that is created in the Doldrums, the region 10 degrees North of the equator, or about 10-12 degrees south of Hawai‘i. The interaction between warmer air near the equator and colder air from higher latitudes is essential for the formation of the trade winds.
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. Warm air rises near the equator and moves into the upper atmosphere. This would create a North wind, but the Coriolis effect, the rotation of the earth, causes the wind to blow northeast in Hawai‘i. As warm air rises, it cools and sinks back toward the earth’s surface, creating a circulation pattern that drives the trade winds.
The Pacific High is a high-pressure system that helps maintain the strength and direction of the trade winds.
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—often trade wind showers—will hit the North and East side of the islands, especially during the early morning hours. The windward coasts and windward sides are generally cloudier and more humid due to frequent trade wind showers, which are responsible for much of the regular rainfall in these regions. This rainfall creates lush tropical rain forests and beautiful rivers. The proximity to the sea and the islands’ elevation above sea level also play a significant role in influencing rainfall and humidity across the islands. Mount Wai’ale’ale on Kaua’i and Big Bog on Maui are two of the rainiest places on the planet as they receive trade wind driven showers nearly every day of the year.
The Hawaiian archipelago includes several smaller islands, which also experience these climate patterns. 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 trades, the prevailing winds that shape daily life and outdoor activities in Hawaii, blow, while divers and boaters will often flee the Leeward southwestern direction. A calm day at sea is a rare occurrence, making such days especially valued for snorkeling and boating. Hikers and beachgoers know to expect scattered rains on the east sides of the islands during the Summer and dry heat to the west. The trades interact with the ocean’s surface, affecting wave height and water clarity. When winds blow from the opposite direction, such as during Kona wind events, it can dramatically change local weather and surf conditions.
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, the surrounding land and its topography influence the suitability of different activities on each island.
Kona Winds and Their Impact
While the famous trade winds are a defining feature of the Hawaiian Islands, there’s another wind pattern that plays a dramatic role in shaping the islands’ climate: the Kona winds. Unlike the steady northeast trade winds, Kona winds blow from the south and west, bringing with them a surge of warm, humid air that can transform the weather across all the islands.
Kona winds are most common during the winter months, when the trade winds weaken and allow these southerly winds to take over. This shift in wind direction can lead to variable winds and unpredictable weather patterns, especially on the Big Island, where Kona winds often bring large waves and rough surf to the west coast. On other islands like Maui and Oahu, these winds can cause sudden changes in temperature and humidity, as well as periods of heavy rain and even thunderstorms.
The impact of Kona winds is felt most strongly on the leeward areas and windward slopes. As warm air flows in from the south, the windward slopes may experience increased cloud cover and rain, while leeward areas can see a spike in temperatures and drier conditions. The temperature differences between these regions become more pronounced, and the overall climate patterns of the islands can shift dramatically in just a few hours.
Kona wind events are a rare occurrence during the summer months, when the trade winds dominate and keep the weather more stable. However, when Kona winds do occur, they can bring high winds with gusts reaching up to 50 mph or more, leading to significant changes in ocean currents and surf conditions. The west coast, in particular, can see larger waves and stronger currents, making it important for beachgoers, surfers, and boaters to stay alert.
Beyond the immediate weather changes, Kona winds can also cause flooding, road closures, and even damage to buildings due to heavy rain and high wind speeds. The warm, humid air can make the islands feel noticeably different, and the shift in wind patterns is something both residents and visitors quickly learn to recognize.
Understanding the interplay between the trade winds and Kona winds is key to appreciating Hawaii’s unique climate. Whether you’re planning a hike in the mountains, a day at the beach, or simply enjoying the outdoors, being aware of these wind patterns can help you make the most of your time in paradise. So next time you feel a warm breeze blowing in from the south, take a moment to notice the change—Kona winds are just another part of what makes the Hawaiian Islands so dynamic and special.
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