Maui Wind Report

Maui is an island and there are two main areas for wind, windward side gets the onshore wind, and the leeward gets the offshore wind. Of course there are more subtle variations, but knowing this fundamental fact can save your life. Offshore winds can be very dangerous in a kayak, SUP or any small boats including windsurfers and kiters. Even surfers and people floating on air mattresses are at risk. Also experienced sailors and outrigger canoe paddlers can get into trouble in offshore winds. There are hundreds or rescues and interventions each year for watercraft blown away from shore. Windward areas are no picnic either, strong winds intersect the shoreline, and the wind can blow unwary sailors onto land. The wind also interact with the land forms on shore and create eddies and severe gustiness, so take care.

Maui winds are a combination of prevailing trade winds (aka “trades”),  combined with local wind effects caused by Maui’s geography, and thermal Seabreezes etc. Less often we have winds that are generated by low pressure systems (storm activity) examples: kona winds and tropical storms. The wind on Maui will be very specific to each different area. The wind on one side of the island can be blowing in the opposite direction from the wind on the other side. Depending on the activity you have planned, you may be seeking out the windiest spot, or trying to shelter from the wind for a surf session or picnic.

Winter is our rainy season, but that doesn’t mean it rains all the time everywhere. Rather it is a time that the weather can be more unsettled and changeable as storm systems and cold fronts extend far enough south in the Pacific to impact Hawaii. When one of these weather systems affects island weather, it usually means several days with lighter winds, increased humidity and cloudiness with showers and heavier thunderstorms possible. It is unusual for any rain to last more than a few hours, so even on the wetter days, the sun usually shines. Still, about 50% of the time, normal trade wind weather dominates, which means a nice breeze with lots of sun and a few mainly brief and light showers, especially along east sides of the islands and near the mountains. Daytime temperatures are usually in the upper 70’s with lows in the mid to upper 60s at lower elevations. After a cold front, it is possible for temperatures to dip into the 50’s at night and only reach the low 70’s during the day. If you go to the higher elevations on Maui and the Big Island, be prepared for cold temperatures and even snow. Temperatures above 10,000 feet will only reach the 40’s during the day and 20’s at night. At elevations above 12,000 feet it is normal for there to be several inches to feet of snow on the ground most days during the winter as those storm systems produce heavy snowfall at the summits. Those same storm systems are also responsible for frequent large surf along north and west sides of most islands. Surf higher than 25 feet occur many times each winter.

March is still considered to be part of our winter rainy season, but by April, patterns begin to change from the unsettled winter weather to more typical trade wind weather. Still, on average during the spring, about 60-70% of the time we experience tradewind weather. This means a nice breeze with lots of sun and a few mainly brief and light showers, especially along east sides of the islands and near the mountains. Most years, especially in March through early April, some of the tradewinds may become quite strong and blow at speeds of 30 mph and higher for a few days at a time. Daytime temperatures by May are usually in the lower to mid 80’s with overnight lows in the upper 60’s to lower 70’s. If you go to the higher elevations on Maui and the Big Island, be prepared for cold temperatures. Temperatures above 10,000 feet will only reach the 40’s to near 50 during the day and drop into the 20’s at night. At elevations above 12,000 feet it is still possible for snow to occur, even into early May. Large surf episodes can still occur, especially in March.

Summer weather is highlighted by the persistent trade winds which occur about 90% of the time. These winds blowing from the northeast provide a cooling breeze accompanied by the occasional shower. The showers that occur tend to be brief and light in nature and confined to the windward, or east, sides of the islands and near the mountains. Daytime temperatures reach well into the 80’s and even the lower 90’s in some locations, especially the drier leeward sides. Overnight low temperatures are in the 70’s. At higher elevations, such as Haleakala on Maui and Mauna Kea and Mauna Loa on the Big Island, temperatures are much cooler. Daytime highs will be in the 50’s and 60’s, with overnight lows in the 30’s and 40’s. During the 10% or so of the time that the trade winds weaken, it can become rather humid. Hurricane season also begins in June, although it is not until late July and into August that the chances of a tropical system somewhere within the Central Pacific begin to really increase. On average, about 4 to 5 tropical systems occur each year within 1500 miles or so of Hawaii. The vast majority of the time, the storms stay far enough away that no impact is noted in Hawaii. The last time a tropical storm or hurricane came close enough to Hawaii was Jimena in 2003. It did not have a significant impact on the state. Summer is also the peak of our South Shore Surf Season. Large winter storms thousands of miles away in the south Pacific send swells toward Hawaii every week or so. Due to the large distance the swells have to travel, about the largest surf we experience along the south side of islands is 10 to 15 feet.

These months are a transition time between the steady trade wind weather of summer and more unsettled weather during the winter. This is still hurricane season for the Central Pacific and Hawaii. On average, about 4 to 5 tropical systems occur each year within 1500 miles or so of Hawaii. The vast majority of the time, the storms stay far enough away that no impact is noted in Hawaii. The last time a tropical storm or hurricane came close enough to Hawaii was Jimena in 2003. It did not have a significant impact on the state. Typically the threat for tropical systems begins to quickly diminish by early October, however during El Nino periods, the threat can continue well into November. 1982 was a prime example, with Hurricane Iwa impacting Hawaii around Thanksgiving time. Trade-wind weather is still the norm, occurring about 70% of the time but this pattern begins to fail more often during October and November as early winter storms in the North Pacific start reaching farther south. When the trade winds fail, usually for 2 to 3 days at a time, it can become very humid. The threat for heavy showers and thunderstorms are also quite high during these brief periods. In fact, more flash flooding occurs during October than any other month. Still, the majority of the time the weather is dominated by trade-winds, meaning generally sunny conditions with brief light showers typically occurring along windward (east) sides of the islands as well as near the mountains. Daytime temperatures at low elevations during September into early October are still in the upper 80’s to low 90’s at times, but by November, highs are typically more in the mid 80’s. Overnight lows are typically in the 70s. At higher elevations on Maui (such as Haleakala) and the Big Island (Mauna Kea and Mauna Loa) it will be much colder. Daytime temperatures will be in the 50’s with overnight lows in the 30’s. Beginning in October, it is possible for some snow to fall above 12,000 feet on Mauna Kea and Mauna Loa. By November, larger surf episodes are starting to take place along north shores of the islands as storms in the north Pacific are getting strong and sending larger swells our way.

Hurricanes are most likely to occur July through December in Hawaii. Hurricanes bring severe bad weather, flooding rain and potentially devastatingly strong winds. The passing of a Hurricane may last days or up to a week or more. The Hurricanes usually develop far away in the eastern Pacific and we generally get several days or more warning of their approach. So there is usually time to make preparations and even evacuate if necessary. Many Hurricanes come close to Hawaii but are just too far away to have a severe effect, This near-miss scenario, and repeated canceled warnings, can give some people a false sense of security. Until one does hit, and then they may be unprepared. Here’s the link to the National Hurricane Center (NHC)

Offshore wind is inherently dangerous: Never kite in off-shore wind if you have no way to return to shore. For Safety, you always need to be able to drift downwind to a point on land. Offshore winds in a bay:  a small bay that is offshore at the launch, but has another shore with onshore wind, that can be easily reached by downwind body dragging is sometimes acceptable. Never ride in pure offshore winds without a dedicated support boat active on site. Launching in offshore winds is very difficult as winds are usually very gusty. Offshore winds are deceptive; the wind at the shore is usually very different from the wind on the water. People often severely underestimate the wind strength in offshore winds. When you launch/ride in offshore winds there is a greater difficulty returning to the beach afterward. Getting back to the beach may become impossible!