Hawaii - Environment

Mark Twain declared Hawaii to be 'the loveliest fleet of islands that lies anchored in any ocean', and not even thirty years of mass tourism have managed to prove him wrong. Whether your thing is volcano spotting, surfing or just lying back and smelling the orchids, this is the place to indulge yourself.

Hawaii climate is tropical with remarkable differences in climate within short distances. This makes explaining where and when best to go quite tricky.

Overall, summer temperatures between May and October are warmer, peaking in August, and drier than the winter months. February and March are the coolest months when night temperatures on the coast fall to 15°C.

During summer, the north-easterly trade winds are more persistent and constant blue skies are not uncommon for weeks on end. In the winter months, the trade winds are often interrupted by other winds, bringing intervals of widespread cloud and rain. During heavy winter storms, brought on by the onset of Kona winds from the south-west, 3-4 inches of rain can fall in an hour. The windward west coasts are more exposed to these winter storms and often receive their mean rainfall in just a hand-full of these winter storms.

However, the most influencing factor of Hawaii's weather is orographic - caused by the mountains. The higher the mountain the greater the extremes. Thus on the Big Island, the windward coast (north-east) receives an average 130 inches of rain each year whilst the dry leeward coast (west), protected from cloud by the 13,600 feet summits of Mauna Kea and Mauna Loa, receives less than 30 inches. Even the west coast of the Big Island rainfall and cloud cover vary - whilst the coast is mostly sunny and dry, less than 5-miles inland on the slopes of Mt. Hualalai in South Kona, sunny mornings often give way to afternoon mists and light rain enriching the coffee farms. The wettest place on earth is on Mt. Waialele in the centre of Kauai - barely 30 miles to the south, the resort town of Poipu receives just 15 inches of rain a year, whilst the town of Hanalei on the supposed wet north coast receives a bearable 45 inches, much of which falls at night or in winter bursts. Similarly, Waikiki Beach sits in the rain shadow of the Koolau Mountains and receives little rain except in the occasional tremendous bursts of thunderstorms which build up in summer afternoons. Many of these storms leave Waikiki dry whilst the nearby hills are covered in dense black clouds and splattered with rainbows.

Climate also changes 2°C for every 1000 feet making temperatures on Hawaii's highest peak fall consistently below zero in winter resulting in snow. The slopes of upcountry Maui and the Big Island, including Volcano National Park are therefore much cooler than the coast and a light jumper may be necessary in summer evenings with central heating, log fires and jumpers needed in winter. If you plan on visiting Mauna Kea on the Big Island or Haleakala on Maui, you'll be wise to take along a set of warm winter clothes.

Hawaii does receive the occasional cyclone (mostly from July to October, although the official cyclone season ends in January) although these are less frequent than in the southern pacific. The last cyclone of force hit Kauai and Oahu in 1992 to devastating effect. Earthquakes and Tsunamis are unpredictable events that will strike Hawaii and have done so in the past with devastating effect. Hilo on the Big Island has suffered two recent tsunamis, in 1960 and 1946, the latter causing 156 deaths. Signs showing the quickest escape route to high ground are placed at vulnerable locations around the islands.

Sea temperatures fluctuate from a high of 27°C in summer to 23°C in winter. The longest and shortest days are 131/2 hours (summer) and 11 hours (winter).

Typical contrasting temperatures (°F) and rainfall (inches) for the Big Island (similar readings for the other islands)

January - One of the coolest months, cold fronts from the Northwest bring showery weather, with this month the wettest of the year. Clear and warm days prevail between these showery periods. Tradewinds blow only 42% of the time, compared with July's 95%. One of the months to see snow on top of our 10.023 foot Haleakala...which sometimes occurs. Large surf impacts the North and West shores. Sea water temperature averages about 75 degrees F.
January averages for different locations on Maui
Lahaina 82-64 F. (27.8C-17.8C) 3.49" precipitation
Hana 79-64 F. (26.1C-17.8C) 9.45" precipitation

Kahului 80-64 F. (26.7C-17.8C) 4.14" precipitation
Kahului % of possible daytime sunshine: 69%

February - One of the coolest months, with showery weather episodes.....mixed with warm, and sunny days. Light winds generally, but some of the strongest winds of the year reported in the winter month of February. Medium to large surf on North and West shores. Snow falls on Haleakala some years. Tradewinds blow on the average 55% of the time. Sea water temperature averages about 74 degrees F.
February averages for different locations on Maui
Lahaina 80-63 F. (26.7C-17.2C) 2.35" of precipitation
Hana 79-64 F. (26.1C-17.8C) 6.83" of precipitation

Kahului 80-63 F. (26.7C-17.2C) 2.87" of precipitation
Kahului % of possible daytime sunshine: 73%

March - Spring brings increasingly strong Northeast tradewinds, and more showers on the windward sides from Haiku to Hana, and on the upper West side from Napili to Kaanapali. Kihei and Lahaina are generally warm and sunny. Winter storms lose their influence on Maui later in the month. Tradewinds blow on the average 61% of the time. Surf still up frequently on the North and West shores. Sea water temperature averages about 74 degrees F.
March averages for different locations on Maui
Lahaina 83-64 F. (28.3C-17.8C) 1.79" of precipitation
Hana 79-65 F. (26.1C-18.3C) 9.54" of precipitation

Kahului 81-65 F. (27.2C-18.3C) 2.72" of precipitation
Kahului % of possible daytime sunshine: 72%

April - Spring weather pattern has become well established, very few winter type storms ever occur this month. Tradewinds are usually quite strong on the windward sides, and frequently carry moisture in the form of cloudiness and showers with them. Lots of sunshine in the leeward areas. Mild weather prevails from the second half of this month through October. Tradewinds blow on the average 74% of the time. Sea water temperature averages about 75 degrees F.
April averages for different locations on Maui
Lahaina 84-65 F. (28.9C-18.3C) 1.05" of precipitation
Hana 80-67 F. (26.7C-19.4C) 8.95" of precipitation

Kahului 82-66 F. (27.8C-18.9C) 1.84" of precipitation
Kahului % of possible daytime sunshine: 56%

May - Summer starts early on Maui, and May is getting quite warm. The tradewinds are blowing most of the time on the windward sides, but carry less clouds and showers then in April. Winter storms are completely absent....leeward sides are summer-like. Tradewinds blow on the average 86% of the time. Sea water temperature averages about 76 degrees F. (25.6C)
May averages for different locations on Maui
Lahaina 85-67 F. (28.9C-18.3C) 1.05" of precipitation
Hana 80-68 F. (26.7C-19.4C) 8.95" of precipitation

Kahului 84-67 F. (27.8C-18.9C) .62" of precipitation
Kahului % of possible daytime sunshine: 58%

June - Summer is here, with warm and sunny days. June is the driest month of the year. Tradewinds blow almost everyday. The hurricane season begins this month, but rarely will a tropical system come close to Maui in June. Tradewinds blow on the average 91% of the time. Sea water temperature averages about 77 degrees F.
June averages for different locations on Maui
Lahaina 87-68 F. (30.6C-20.0C) .09" of precipitation
Hana 83-69 F. (28.3C-20.6C) 3.85" of precipitation

Kahului 86-69 F. (30.0C-20.6C) .27" of precipitation
Kahului % of possible daytime sunshine: 79%

July - Summer fully engaged weatherwise, with warm to very warm temperatures. Fortunately the tradewinds temper the summer-time heat. These cooling and refreshing winds keep Maui feeling comfortable during the long warm summer months. Very infrequently a tropical storm may move close to the area giving sticky weather and showers. Summer is when Maui sees small -medium size waves rolling onto the South facing shores from Lahaina to Wailea. These waves are generated in the Southern Hemisphere down near New Zealand...where winter storms "down under" send waves 1000's of miles....to arrive here as South swell. Tradewinds are blowing on the average 95% of the time. Sea water temperature averages about 78 degrees F.
July averages for different locations on Maui
Lahaina 88-69 F. (31.1C-20.6C) .17" of precipitation
Hana 88-70 F. (28.3C-21.1C) 5.60" of precipitation

Kahului 87-71 F. (30.6C-21.7C) .38" of precipitation
Kahului % of possible daytime sunshine: 69%

August - Warm, sunny to partly cloudy days are the rule for August. Tradewinds are still fanning the island with great regularity. Occasionally a tropical storm or Hurricane will get close enough to Maui to cause our winds to stop and the humidity to rise to uncomfortable levels, though it is unusual. Small-medium size waves continue to be at times a problem...in that, the South shores, where these waves impact, are the same beaches that the visitors (who often are not used to waves of any size) are at play and sunbathing. Persons should be careful during these periodic high surf events. Tradewinds are blowing on the average 94% of the time. Sea water temperature averages about 79 degrees F.
August averages for different locations on Maui
Lahaina 88-69 F. (31.1C-20.6C) .18" of precipitation
Hana 84-71 F. (28.9C-21.7C) 5.62" of precipitation

Kahului 88-71 F. (31.1C-21.7C) .49" of precipitation
Kahului % of possible daytime sunshine: 73%

September - The weather continues to be very warm, the height of summer here in the tropics. Some of the highest temperature readings of the season occur in this month. Tropical Storms and Hurricanes rarely enter Hawaiian waters, but this is the month when they come the closest and are more apt to affect the weather on Maui. Normally they stay far away, but when they get close enough to the island, they make the residents uncomfortable with the muggy atmosphere they produce. Hurricane Iniki entered into the adjacent waters, and impacted the island of Kauai in September of 1992. Tradewinds blow on the average 83% of the time. Sea water temperature averages about 80 degrees F.
September averages for different locations on Maui
Lahaina 89-70 F. (31.7C-21.1C) .34" of precipitation
Hana 84-70 F. (28.9C-21.1C) 5.38" of precipitation

Kahului 88-70 F. (31.1C-21.1C) .35" of precipitation
Kahului % of possible daytime sunshine: 62%

October - This is the month that temperatures begin moderating from summers high heat a little! Tradewinds also begin to fade from the island weather scene. In some years, Maui begins to see the first winter-like storms that are far out to sea in the North Pacific......they sometimes can produce the first large waves of the season. Occasionally one of these early winter storms will send a weak cold front through the islands, which can cause a few showers. This month is still mild and dry. Tradewinds are blowing on the average 71% of the time. Sea water temperature averages about 79 degrees F.
October averages for different locations on Maui
Lahaina 88-69 F. (31.7C-20.6C) 1.09" of precipitation
Hana 83-70 F. (28.9C-21.1C) 7.02" of precipitation

Kahului 87-69 F. (30.6C-20.6C) 1.23" of precipitation
Kahului % of possible daytime sunshine: 60%

November - Generally a transition month between summer and winter, with weather of both seasons common. The first real winter storms to the North and NW send down a cold front or two, with some showery spells, especially after the middle of the month. Winter storms also more regularly send large waves onto the North and West shores. Temperatures begin to dip noticeably (before you start packing your down jackets....please realize that when I say "dip down", I mean from the high 80's down to the middle 80's! :-). November in some years begins the rainy season. Tradewinds are blowing on the average 64% of the time. Sea water temperature averages about 77 degrees F.
November averages for different locations on Maui
Lahaina 86-67 F. (30.0C-19.4C) 2.15" of precipitation
Hana 81-68 F. (27.2C-20.0C) 8.67" of precipitation

Kahului 84-68 F. (28.9C-20.0C) 2.59" of precipitation
Kahului % of possible daytime sunshine: 67%

December - A winter month on Maui, with fairly frequent cold fronts sweeping over the island, bringing showery periods, with sometimes gusty winds. Still, December has its fair share of warm and balmy days as well! Medium to large surf is very common on the North and West shores of the island. One of the wettest months of the year, with some rainy days....although the areas around Kihei and Lahaina on the leeward sides of the island see less moisture than do the wetter windward sections in general. Tradewinds are blowing on the average 57% of the time. Sea water temperature averages about 76 degrees F.
December averages for different locations on Maui
Lahaina 83-65 F. (28.3C-18.3C) 3.20" of precipitation
Hana 79-66 F. (26.1C-18.9C) 6.05" of precipitation

Kahului 81-66 F. (27.2C-18.9C) 3.27" of precipitation
Kahului % of possible daytime sunshine: 58%

When To Go To Hawaii

Hawaii's weather is pleasant year-round. Tourism peaks in the winter months from November to March - this is when mainland Americans, in particular retires, take their extended winter break. In these months, accommodation can be booked-out well in advance. Winter is also the peak season for surfing and whale watching making the north shore of Oahu and Maui popular destinations. The summer months are drier and slightly warmer (about 30OC), the seas and surf are generally calmer and this is the Hawaii holiday season popular with families. The low seasons when hotel prices are most likely to be discounted is between April-May and September-October.

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