Most people don’t fly to Hawaiʻi expecting altitude sickness to be on the packing list. You’re going to the beach, right? The trouble is two marquee summit experiences put you higher than the rim of the Grand Canyon, high enough that a chunk of visitors get hit with the same headache, nausea, and brain-fog they’d feel at a Colorado ski resort.
Mauna Kea on the Big Island tops out at 13,803 feet. Haleakalā on Maui reaches 10,023 feet. Both are reachable by road, though only Haleakalā is a standard rental-car drive (Mauna Kea’s summit road is 4WD-only and off-limits to most rental contracts — more on that below). Mauna Kea is roughly a two-hour drive from sea level in Hilo to the summit, plus a required acclimatization stop. Haleakalā runs about two hours from Kahului. Either way, your body goes from beach to thin air faster than it likes.
This isn’t a reason to skip either trip. Both are worth doing. But altitude on a Hawaiʻi vacation catches a lot of travelers off-guard, partly because nobody warns you in the rental car line at OGG. Here’s what to actually expect.
