Humuʻula–Mauna Kea Summit Trail
Humuʻula–Mauna Kea Summit Trail information
This daunting, all-day hike starts at 9200ft, then climbs almost 4600ft over the next 6 miles to Mauna Kea's summit. Expect thin air, steep grades and biting weather on this utterly exposed trail, where it often feels like you're going to step off the mountain into the sky. Plan on eight hours for the round-trip hike and bring a gallon of water per person – dehydration is a real danger at these altitudes. Don't hike in inclement weather.
Start very early – by 6am if possible. It typically takes five hours to reach the summit, and half as long coming down, and you want time to explore in between. Consult rangers for advice, and get a map and register at the Visitor Information Station’s outdoor trail kiosk before hiking. Be prepared for serious weather – snow and 100mph winds are possible.
Park at the Visitor Information Station and walk 1000ft up the road. Where the pavement ends, go left on the dirt road, following several Humuʻula Trail signs to the trail proper. Reflective T-posts and cairns mark the route. After about an hour the summit road comes back into view on your right, and the vegetation starts to disappear. As you weave around cinder cones and traipse over crumbled ʻaʻa and slippery scree, you pass various spur trails, which all lead back to the access road.
Most of the way you will be passing through the Mauna Kea Ice Age Natural Area Reserve. After about three hours a sharp, short ascent leads to Keanakakoʻi. The hardest, steepest part of the trail is now behind you. After another mile you reach a four-way junction, where a 10-minute detour to the left brings you to Lake Waiʻau. Return to the four-way junction and head north (uphill) for the final push to meet the Mauna Kea Summit Rd at a parking area. Suddenly the observatories are visible on the summit, and straight ahead is ‘Millimeter Valley,’ nicknamed for its submillimeter and millimeter observatories. The trail officially ends at the access road’s mile marker 7, but the true summit still snickers at you another 1.5 miles away.
For Native Hawaiians, the summit is a region, a realm, not a point on a map. But if you really need to place a boot toe on Puʻu Wekiu, Mauna Kea’s true summit, soldier on till you reach the UH 2.2m Telescope, where the short spur trail to the summit begins.
When descending, return along the shoulder of the access road rather than retracing the trail. Though the road is 2 miles longer, it’s easier on the knees and easier to follow as sunlight fades. Also, it’s common for hikers to get offered a lift downhill; sticking to the road increases your chances.
Alternatively, save time and energy by hitching a lift to the top from the Visitor Information Station and just walking down (about three hours).