Hawaii, the oceanic American state is tropical but encounters four different Köppen climate zones: tropical, arid, temperate and polar based on altitude and topography on the constituent islands. The entire state is an archipelago surrounded by water, which lies in Oceania, southwest of the continental United States in the central Pacific Ocean. Trade winds from the Pacific Ocean substantially influence the weather as they push towards the northeastern slopes of the Hawaiian Islands where they move further upwards and produce significant rainfall on the windward side.
The eight main islands have varied microclimates such as tropical rainforest, arid desert, temperate and alpine based on the region's elevation and its relative position, windward or leeward with respect to the high mountains. The diverse terrain of high mountain peaks up to 4200 meters, valleys, ridges, and extensive slopes is responsible for wide-ranging weather conditions. The vast Pacific Ocean that surrounds Hawaii on all the sides supplies large quantities of fresh sea air throughout the year and acts as a giant thermostat that does not allow the temperatures of the islands to reach the high levels typical of the tropics. Hawaii's climate is characteristically tropical but with moderate temperatures and humidity due to the influence of north and eastern trade winds.
Summer average high temperatures peak around 84°F (28.9°C), as highs usually do not breach 90°F (32.2°C), while the lows seldom drop below 70°F (21.1°C). Winter average high temperatures are usually around 79°F (26.1°C), and the lows seldom dip below 65°F (18.3°C) at night. Hawaii has the lowest record high temperature at 100°F (37.8°C) and is the only American state never to record a temperature below 32°F (0°C). Snow falls at higher altitudes such as Mauna Kea and Mauna Loa in the winter. Mount Waialeale on Kauai records an average annual rainfall of about 460" (11684mm) per year, which is the second-highest average annual rainfall on Earth.
The Hawaiian Islands mainly exhibit two seasons: dry from May to September, which is hot and receives a minor amount of rain and wet from October to April, which is warm and aggregates majority of the annual precipitation of 32" (812.8mm). Proximity to the equator gives equal days and nights with minimum temperature variations at sea level.
Pacific hurricanes that are a threat from July to December seldom affect the state to a major extent. Thunderstorms are a bigger threat that drives big waves towards the islands but localized weather patterns mean there is always a possibility to find cool, sheltered beaches at any time of the year - it is common for a region to experience heavy rainfall while it may be sunny at the same time a few miles away from it.
The best time to visit Hawaii
Hawaii is popular, around the year tourist destination with its vast coastline of about 750 miles, diverse landscape amid a backdrop of mountains, warm tropical climate, and abundant public beaches. However, the best time to visit Hawaii is from May to October in the dry season, particularly in May and June, as the summer temperatures are not extreme due to trade winds and the surrounding abundant waters. July to December sees a regular threat of thunderstorms, and hurricanes though not destructive, occur in this period.
The worst time to visit Hawaii
Hawaii has comfortable temperatures and sunny days regularly in the winter. Nevertheless, the period from November to April in the wet season is prone to heavy rainfall and is the worst time to visit Hawaii compared to the rest of the year. The windward areas on the northern mountain slopes get ample rainfall, and the hurricane and storm season stretches until December. Most of the tourist resorts are on leeward sides, which mean less rain and cooler temperatures - hence flights and accommodation tend to be costly from November to April.
Hawaii is prone to regular thunderstorms and hurricanes from July to December. Winds blow up to 100mph (160.9km/h) with severe rainfall and lightning during severe thunderstorms. Pacific hurricanes do not have a high impact but cyclones from northerly latitudes and Kona storms near the islands that last for several days pose routine threats from October to March. The winter experiences more clouds, rainfall, and storms as well as south and westerly trade winds. Hailstorms are more frequent than tornadoes, which have an annual average of one per year.
Weather in January
January lies in the wet season with average temperatures in the mild range of 68°F (20°C) to 79°F (26.1°C). Temperatures tend to be slightly lower on the leeward slopes compared to the windward areas. Honolulu is the warmest in the 66°F (18.9°C) to 81°F (27.2°C) range while Hilo on the coast, exposed to northeast trade winds measures 64°F (17.8°C) to 79°F (26.1°C). Mauna Kea, at 4200 meters is usually the coldest around 27°F (-2.8°C) to 43°F (6.1°C) as snowfall is regular in the winter at higher elevations. Windward regions, especially mountain slopes around 2000 to 3000 meters have pronounced rainfall in the wet season. While rainfall averages 3" (76.2mm) in the state of Hawaii in January, it registers around 9.3" (236.2mm) on the coast. The sun shines brightly for 7 hours a day on the leeward side even in the winter, which is the location of a majority of the tourist resorts. No wonder that Hawaii is a hotspot - at any time of the year, there is always a place that has pleasant weather conditions! Watch out for the crowds as tourists throng every nook and place during the New Year!
Weather in February
February is the coldest month of the year in Hawaii with the average temperatures in a steady 68°F (20°C) to 79°F (26.1°C) range. Cold fronts are common that precede a cold wave from the northern Polar Regions - however, the considerable distance that any air mass has to travel to reach the islands reduces its intensity so that temperatures are never extreme. Instead, localized weather patterns matter more, as the temperatures register a freezing 27°F (-2.8°C) to 43°F (6.1°C) in the mountains to a steady range of 66°F (18.9°C) to 81°F (27.2°C) in the leeward areas at sea level. Average sea temperatures are at a warm 74°F (23.3°C), and it is fit for swimming, sailing, snorkeling and other water activities that are rarely possible elsewhere in the United States during the winter. Keep an eye on the weather for thunderstorms, as they are common in February. Volcanic fog is a phenomenon to be aware of while exploring the active volcanoes of Hawaii!
Weather in March
March is a wet month with average rainfall to the tune of 3.4" (86.4mm) and temperatures in the agreeable 70°F (21.1°C) to 79°F (26.1°C) range. Significant rainfall occurs in the highlands and forested areas, but it mainly occurs on the northern and eastern sides exposed to trade winds. Northern cold winds do not find much strength to reduce the temperatures by more than a few degrees. The sun shines on the south and western areas of the islands prominently up to 8 hours a day. The temperatures in places like Honolulu are in a pleasant 68°to 81°F (27.2°C) range while north and eastern mountains are around 27°F (-2.8°C) to 52°F (11.1°C) and the coasts are between 64°F (17.8°C) to 79°F (26.1°C). For people who wish to see snow, the peaks of Mauna Kea, Mauna Loa, and Haleakala offer excellent opportunities during the cold months - the rainfall at the peaks is scanty while it is heavy a little further down the slopes on the north and eastern sides of the mountains.
Weather in April
April is a beautiful month that brings the end of the wet season in Hawaii with partly cloudy skies and average temperatures in the temperate 70°F (21.1°C) to 79°F (26.1°C) range. An average rainfall of 2" (50.8mm) registers on the rain gauge - heavy rain occurs in the highlands, moderate in the lowlands of north and east and meager in south and west. Much of the rain falls during the nights while islands with flat terrain such as Niihau are arid and receive scanty rainfall. April sees the end of thunderstorms, and high wind speeds as the temperatures remain steady around the 66°F (18.9°C) to 79°F (26.1°C) range on the coast, without the threat of large ocean waves. Overall, Hawaii has pleasant weather for tourists most of the time, be it enjoying the sunshine, lying on the beach or exploring the mountains and tropical forests. A light sweatshirt is a good idea while strolling on the beaches and enjoying the warmth of the sea in a sheltered beach.
Weather in May
May is a wonderful time to visit Hawaii that begins the dry season, and the average temperatures rise to the 72°F (22.2°C) to 81°F (27.2°C) range. A drop in cloud cover, particularly at the mountain peaks, and humidity level are the features of the dry season as the sun returns to full duty with average sunshine of 10 hours a day. A constant supply of fresh ocean air keeps the temperatures moderate and unvarying over long periods. Showers are frequent on the windward side of coasts such as Hilo, which accumulates 8.1" (205.7mm) in May where average temperatures are around 66°F (18.9°C) to 81°F (27.2°C). Light clothing is the order of the day except for botanists and researchers who explore the tropical rainforests in the highlands. Caution - do not take the Hawaiian sun lightly due to the moderate temperatures as the sun rays are intense and there is a lack of humidity; use plenty of sun protection.
Weather in June
June is another fascinating month to visit Hawaii with average temperatures in the comfortable 73°F (22.8°C) to 82°F (27.8°C) range. Trade winds flow from the area of high pressure, the North Pacific High, which lies in the north and east of Hawaii in the summer and forms a ventilation system with mild temperatures around the islands. As such, the north and east coasts have mild average temperatures around 68°F (20°C) to 82°F (27.8°C) in June and draw many tourists in the dry season. The reefs have calm and clear waters with the average sea temperature around 74°F (23.3°C) that creates interest in snorkeling and scuba diving activities. Night temperatures around the ocean hardly vary around 2°F (-16.7°C) to 4°F (-15.6°C) from the day, which sees the tourists gazing at the stars in cloudless skies after sunset. The amount of sunshine is good throughout the year, especially in the leeward areas; Hawaii receives an average of 10 hours of brilliant sunshine in June.
Weather in July
July is a summer month in Hawaii that lies in the dry season with average temperatures around 75°F (23.9°C) to 82°F (27.8°C). It also brings thunderstorms to the region mainly due to localized weather patterns that bring winds, lightning and sometimes hail along with them. Waterspouts are common in inland areas of the islands. The south and western sides of the islands are more sunny and dry and enjoy comparatively lesser storm interference. Honolulu on the leeward side has temperatures in a warm range of 75°F (23.9°C) to 88°F (31.1°C) in July. Explorers and mountain hikers need to pack a raincoat or umbrella, as convectional rainfall is standard on the mountain slopes in the summer. On an average, the sun is present on the horizon for 10 hours a day in Hawaii. Just keep an eye on storms to enjoy the fantastic sailing and surfing opportunities available in the warm waters.
Weather in August
August is the hottest month of the year in Hawaii with the average temperatures in a high range of 75°F (23.9°C) to 84°F (28.9°C). Few days cross the 90°F (32.2°C) barrier, and it is rare to have a day around 95°F (35°C). August is also the driest and the least humid month with an average of 1.3" (33mm) of rain. The difference between high temperatures on the coast at Hilo and the southwest at Honolulu is around 8°F (-13.3°C); while Hilo receives 9.8" (248.9mm) of rain in August, Honolulu accumulates only 0.6" (15.2mm). Hawaii sees such microclimatic differences throughout the year and hence is a popular tourist destination with a time and place for everybody. Additionally, hurricanes common of equatorial waters do not affect Hawaii mainly due to its local weather patterns and the vast distance from main continental lands. The sun is never out of its place for extended periods, and there is never a true off-season to get cheap flights and accommodations.
Weather in September
September is a summer month with the heat in the average 75°F (23.9°C) to 84°F (28.9°C) range with very few days around 90°F (32.2°C). While the temperatures in the low lands are sunny, the mountain slopes exposed to the trade winds see low temperatures in the average range of 32°F (0°C) to 55°F (12.8°C). The active volcanoes around Hawaii such as Molokini attract many tourists, as do the tropical rainforests of the highlands - September days are perfect for such hikes as the rainfall is relatively smaller than the wet season and the temperatures are comfortable although nights are usually around freezing. Keep in mind that temperatures decrease with a rise in elevation and plan to return by the end of daylight. Winds are less troublesome on the leeward sides of the mountains and at higher altitudes. Spectacular views of the surrounding landscape abound from the mountain peaks, which is worth the efforts of hours of ascent in the backdrop of the sunny weather.
Weather in October
October is a transitional month in Hawaii with average temperatures in the warm 75°F (23.9°C) to 84°F (28.9°C) range. Rain averages about 3.1" (78.7mm) and the start of the season of the local Kona storms brings along strong winds and lightning. The storms sometimes bring rain that lasts up to several days. Dry areas typically see a majority of their annual rainfall during such storms. The change in tidal patterns in the Hawaiian waters create legendary ocean waves often seen in movies and heard in folklore - it is a major attraction for surfers and extreme sports lovers from all over the world. The sea temperature rarely crosses 80°F (26.7°C) and is a perfect combination along with the swelling of water towards the islands. The sunshine lasts for an average of 8 hours a day in October, so there are numerous sunny days to spend on the beautiful beaches amid a plethora of activities.
Weather in November
November is usually the wettest month of the year in Hawaii with an average rainfall of 4.9" (124.5mm). The average temperatures are in the mild 73°F (22.8°C) to 81°F (27.2°C) range with the Pacific High moving a little southward by the end of the summer. The effect of northeastern trade winds reduces to an extent but the overall vast bodies of water surrounding the island ensure that there is minimal variation in temperatures. Coastal areas are dry, but mountain slopes see a substantial amount of rain in November. Mauna Kea Observatory registers an average temperature of 28°F (-2.2°C) to 45°F (7.2°C) with most of the nights in the winter below the freezing point. It is not a great idea to explore the mountains during the winter due to the rain, the increase in humidity and fog, as well as the presence of more sunny weather in the lowlands - Honolulu, averages 7 hours of average sunshine during November!
Weather in December
December is a winter month in the wet season of Hawaii that sees a major rise in the tourist numbers. Average high temperatures are around a mild 79°F (26.1°C) while average low temperatures drop to a comfortable 70°F (21.1°C). There are many sunny days on the leeward side of the mountains where the rainfall mostly occurs during the wet season. Honolulu averages 68°F (20°C) to 81°F (27.2°C) while Hilo on the coast is a bit lower in the 64°F (17.8°C) to 79°F (26.1°C) on the windward side. The mountains touch a high of 43°F (6.1°C) to 50°F (10°C) while the lows are in the cool range of 28°F (-2.2°C) to 36°F (2.2°C). The plateau area at a lower elevation of 2000 meters registers a temperature range of 41°F (5°C) to 66°F (18.9°C). Rainfall differs from 3.1" (78.7mm) on the leeward side to 11.6" (294.6mm) on the coast while the mountain peaks receive little rain. December experiences frequent thunder and Kona storms with wind speeds of 60 to 100mph (160.9km/h). Light clothes in the day with a scarf for the wind and a light jacket or raincoat are mostly sufficient at lower elevations. [Resources]
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