Kaua‘i doesn’t have the best weather in the state, but the best weather in the state is on Kaua‘i. What do we mean by that? Well, when it’s good here, it’s as good as weather can get—brilliant sunshine, crystal clear air, and gentle but constant breezes. That’s when it’s good Kauai weather.
Yeah, but I’ve heard it always rains on Kaua‘i. We heard this many times before we came here for the first time. The reality of Kauai weather is that it has more rainfall than the other Hawaiian islands. In fact, one of the rainiest spots on earth is smack dab in the middle of the island. Mount Wai‘ale‘ale is an undisputed year-round rain magnet, receiving around 400 inches per year, which is a staggering 33 feet annually. (Though they’ve measured rainfall there for over a century, stating an average is more of an art than a science since there were times in the past they went up to read that gauge, perhaps after a year, only to find it overflowing—so they guessed. Also, it varies a lot. In 2018 it got 519 inches!)
The mountain is shaped like a funnel pointing directly into the moisture-laden trade winds, which are forced to drop their precious cargo during their march up the slopes. The summit of Wai‘ale‘ale is other-worldly, with plants stunted and dwarfed by the constant inundation of rain. Moss, fungi and lichen flourish in the swamp just west of the actual peak. Alaka‘i Swamp contains flora and fauna found nowhere else in the world. On the opposite side of the mountain, the spent clouds can do no more than drift by, making the west side of the island rather arid. What rain it does get comes from the sporadic Kona winds. (Throughout the islands, Kona winds refer to winds that come from the southwest and are often associated with inclement weather.)
All that said, the odds are overwhelming that rain will not ruin your Kaua‘i vacation. The coast gets far less rain than the waterlogged central interior, and throughout Kaua‘i the lion’s share of rain falls at night. When it does rain during the day, it is usually quite short-lived, often lasting a matter of a few minutes. One of the things that takes a little getting used to is the fleeting nature of Kauai weather here. In many parts of the country, rain or sunshine are words used by themselves to describe the Kauai weather that day. On Kaua‘i, a warm, passing shower is to be expected and rarely signifies that a long period of rain is to follow. If you call the local telephone number for the National Weather Service (808-245-6001), you will probably hear something like this. “Today—mostly sunny, with a few passing windward and mauka (mountain) showers. Tonight—mostly fair with a few passing windward and mauka showers. Tomorrow—mostly sunny, with a few passing windward and mauka showers.” So don’t get bummed if it suddenly looks ominous in the sky. It’ll probably pass within a few minutes, leaving happy plants in its wake.
If you want to know whether to take the top down on the convertible, look into the wind, and you’ll be able to see Kauai weather coming. Dark clouds drop rain—the darker the cloud, the harder the rain. It’s as simple as that, and you will often see locals looking windward if they feel a drop on their heads. If you’re inland, you will often be able to hear the rain approaching. When you hear the sound of a rushing river but there isn’t one around, take cover until it passes. (Mango trees are ideal for this purpose and have ancillary benefits, as well.)
In planning your daily activities, a good rule of thumb is that if it is going to be a rainy day, the south shore will probably be sunny, and the west shore will almost certainly be sunny. The exception is during Kona winds when Kauai weather is the opposite of normal.
Storm systems do discover the state from time to time. Sometimes they’re here for days. If one happens to hang around during your trip, don’t despair. I first met Kaua‘i during one of the wettest times in decades. There was even lightning, which is rare. And it was during that stay that I fell in love with the island and vowed to make it my home. Kaua‘i in the rain is still Kaua‘i.
As far as hurricanes are concerned, don’t waste your time worrying about them. It’s true, we had a real ‘okole kicker back in 1992. Hurricane ‘Iniki was a category 4 storm that stripped the island bare, ironically striking on September 11th of that year. But after this pruning, the island recovered and became greener than ever. Hurricanes are few and far between here. The only previous hurricanes to hit the island last century were ‘Iwa in 1982 and Dot in 1959. When Isabella Bird traveled here in 1873, where she penned her excellent book, Six Months in the Sandwich Isles, she reported that “hurricanes are unknown in the islands,” which means that there hadn’t been one in living memory. (Of course, if one does strike during your stay, kindly disregard this last statement.)
As far as temperatures are concerned, Kauai weather is incredibly temperate. The average high during January is 78 °F, whereas our hottest time, late August/early September, has an average high of 85 °F. With humidity percentages usually in the 60s and low 70s, Kaua‘i is almost always pleasant. The exception is the extreme west side, which is about 3 degrees hotter. (That might not sound like much, but you sure do notice it.)
Kaua‘i’s surface water temperatures range from a low of 73.4 °F in February to a high of 80 °F in October. Most people find this to be an ideal water temperature range. (Ocean water near a river mouth, such as Lydgate Beach Park, can get colder—we’ve seen the ocean get as low as 70 °F there during unusually cold Februarys.)
To get current Kauai weather or ocean information, call the National Weather Service Weather Forecast (808-245-6001).
For more info on Kauai Weather, download our Hawaii Revealed app.