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Hawaii Weather Information
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Hawaii weather 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 15C.
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 Kaua'i - 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 2C 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 Kaua'i 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 27C in summer to 23C 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)
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Hilo - East - Windward |
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Kona - West - Leeward |
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day/night
(F) |
Rain
('' / month) |
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day/night
(F) |
Rain
('' / month) |
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| Jan-Mar |
79 / 62 |
11 |
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80 / 62 |
4 |
| Apr-Jun |
80 / 62 |
15 |
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81 / 65 |
2 |
| Jul-Sep |
82 / 70 |
10 |
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82 / 68 |
0 |
| Oct-Dec |
80 / 65 |
15 |
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81 / 63 |
1 |
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