Vacation Rental in Princeville Kauai

and Kauai Travel Guide

©B.Pruitt 2009-2012

Climate of Kauai and Hawaii

It’s hard to imagine a climate more agreeable than Kauai’s.  Daytime high temperatures consistently reach the 80s, cooling to the high 60s at night.  Sunshine is plentiful and the humidity is moderate.  In fact, the climate is a principal reason Kauai attracts more than a million visitors a year.

Kauai experiences only two seasons, summer and winter.  The warmest months are August and September and the coolest months are January and February, but the average maximum temperature between the warmest and coolest month only ranges seven degrees.  The least precipitation falls from June to September and the rainiest months are December to February.  These are averages and trends however; hot, dry days and cool, wet days will occur in every month.

Kauai’s equable climate is credited to a number of factors.  Its location is tropical; the 22nd latitude north of the equator bisects the island.  The vast waters of the Pacific Ocean, which act as a climatic thermostat, warming cool air masses and cooling warm air currents, surround the Hawaiian Islands.  Ocean temperatures around Kauai range from 76-79°F.  As well, the Trade Winds, which regularly blow at 10-20 mph, provide a moderating effect on the temperature and humidity.  The average relative humidity at Lihue is 75 percent.  In fact, after measuring humidity data for 40 years, the average monthly relative humidity there has never varied more the 3.5 percentage points.  In the Hawaiian Islands, the Trade Winds occur well over 50 percent of the time with this figure exceeding 90 percent in the summer.  Sometimes the Trade Winds are replaced by kona winds, which can carry rain and uncomfortably humid weather from the southwest.

Despite a lack of strong seasonal variation, Kaua‘i is host to an extraordinary diversity of microclimates, from desert to rainforest.  Temperature drops three degrees for every 1,000 feet of altitude.  This is a factor you are sure to notice when you drive to the Kalalau Valley lookout and gain more than 4,000 feet of altitude in just 18 miles.  Rainfall varies more with location than with season.  The northeast shore is the windward side of the island when the Trade Winds are blowing.  When the winds, laden with moisture, blow over the island they are forced up by the land.  As the temperature of the air drops with altitude so does its ability to hold moisture.  The moisture in the cooler air condenses into rain, mainly in the higher altitudes of the windward side.  The air, depleted of much of its moisture, is pushed over the mountains, warming as it descends to the island’s leeward side.  The sunshine-drenched resort of Poipu is in the lee of the Hā‘upu (Hoary Head) Ridge.  The extinct volcano that formed Wai‘ale‘ale traps most of the moisture headed to the towns of Waimea and Hanapepe and the sugar cane fields of southwest Kauai.  Hanalei, on the windward side of the island receives four times as much rain as Kekaha.

Some very wet years in the 1960s caused the average annual precipitation measured at the rain gauge at Mt. Wai‘ale‘ale to be listed at 460 inches.  Since then, every guidebook, brochure and tour guide has called Mt. Wai‘ale‘ale the "wettest spot on earth."  More recently, Wai‘ale‘ale's average precipitation has been between 350 and 400 inches—still voluminous by any standard.

It rains every day somewhere on Kauai.  Most rain showers are isolated and of short duration.  Severe storms can occur, particularly in the winter.  If you plan on hiking in the backcountry, especially the Na Pali trail, pay heed to flash flood warnings given in local weather forecasts.

Winter storms in the north Pacific create swells and large surf on Kauai’s North Shore.  Twenty-foot waves are possible.  They are extremely dangerous, but from a safe distance they provide spectacular ocean watching.  Hurricanes and tsunamis are possible but rare.  Weather forecasts can warn of approaching hurricanes several days in advance.  Tsunami warning sirens are positioned throughout the island.  They are sounded as a test at 11:45 a.m. on the first government workday of each month.

The hurricanes and tropical storms that affect Hawaii usually originate off Mexico or Central America.  As they head west, they usually travel to the south of Hawaii or dissipate over cooler ocean water if they turn north.  Hurricane season in Hawaii is July to November.  Hawaiian names are given to hurricanes when they pass within 1,000 miles of the Hawaiian Islands.  Five named hurricanes have affected Kauai in the last half of the twentieth century.  Three hurricanes struck Kauai in the 1950s, causing two deaths.  In 1982, Hurricane Iwa had sustained winds of 81 m.p.h., with gusts up to 117 m.p.h., resulting in one death and more than $200 million in damage.  The most devastating hurricane was Iniki, which struck in 1992.  Its winds and rain took 8 lives and caused $1.9 billion in property damage.

In 1957, a major tsunami that originated in the Aleutians, hit Kauai's north shore.  In the town of Hā‘ena, the sea rose more than 32 feet above normal.  Only four of the 29 homes in the small community were left standing after the waves.  The surging water virtually wiped out the villages of Wainiha and Kalihiwai and the North Shore was isolated for days as bridges and roads were destroyed.

Good weather is far more likely to embrace you than bad weather.  You can appreciate the weather even more during your visit as you scan the newspaper for temperatures back home.

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