First and foremost we need to point out there are two distinct parts of West Kauai. The Southwest portion of Kauai beyond Waimea Town (along Highway 50), and the Northwest portion (along Highway 550) that borders the Na Pali coast region including Koke'e and Waimea Canyon State Park. We have not separated these areas on the map because they are all accessible from the roads in West Kauai, as a single region. We have however split their individual descriptions and attractions below for clarity.
For the most part, Northwest Kaua'i is impassable, filled with mountainous terrain and valleys that make roads impossible to build here. This side of Kaua'i is most famous for the Na Pali coast (which we've split into it's own region) and the trails and hikes that stretch far and wide across it. Specifically, our definition of Northwest Kauai is two state parks, Koke'e and Waimea State Parks along highway 550 to be exact.
You've probably heard the most about this region because of Waimea Canyon, which Mark Twain called, "The Grand Canyon of the Pacific."
It is indeed a beautiful sight to behold, and you have several overlooks to enjoy it from. The region is a mecca to hikers, offering dozens of trails from the most challenging to quite easy. You can hike down into Waimea Canyon (all the way to the Waimea River), hike behind Kalalau Valley in the Alakai Swamp (the world's highest swamp), or head out on a trail to one of the back rims of a Na Pali valley.
The elevation of Northwest Kauai is significantly higher than that of all other Kauai regions and areas. While starting near sea level in Waimea town, highway 550 climbs to nearly 4,200 feet by the end of the highway at Pu'u o Kila overlook. This region is thus generally much chillier than the rest of the island, and a light jacket is a good idea for early morning adventures.
Weather wise, the Waimea and Koke'e State Park area is a mix of wet and dry, with trails toward the Pali coast being drier than those heading inland. The Alaka'i Swamp trails are typically on the wetter side, so don't be surprised by the occasional storm. The swampy conditions are also due to the rainfall that occurs on the mountains to the east of the swamp and then flows down into this area of Kaua'i. In the valleys of Na Pali, which are skirted by Koke'e trails on the rims above, rain can come down in buckets at any given time as clouds fill in between the ridged valley walls. These clouds often build up in the valleys and flow over the back walls, giving the "fog-machine" appearance in Northwest Kauai.
Northwest Points of Interest
Popular NWest Kauai Attractions
Southwest Kaua'i includes the Waimea town area, Hanapepe town, and Polihale Beach State Park. The weather on this side of the island varies greatly. Here on the southwest side, it is incredibly dry. Just north, along the Na Pali coast (and within Northwest Kauai), the rain is significantly heavier. On average, the weather at the coast and near Waimea Canyon is hot (75-80F) and dry with about 25 inches average rainfall a year.
The southwest is pretty remote in comparison to the rest of the island. It's usually sunny when you're not heading mauka (inland) and dry most days of the year on the coast. The town of Waimea leaves a lot to be desired for most visitors, but to the people that call it home, it's, well, home. The road from Waimea heading towards Polihale will leave you wondering what continent you're on. It turns to dusty desert in this area. The Barking Sands Pacific Missile Range is also located on the west coast of Kaua'i. This is a naval base out in the middle of nowhere on an incredibly long and vacant beach. From near Polihale you can see where they've bored into the ancient cliffs to store military supplies - and we're just fine with not knowing what.
All the towns in West Kauai are within the southwest portion of the region - including Eleele, Hanapepe, Kamakani, Port Allen, Kapaka, and Mana.