Maunakea is the tallest mountain on earth measured from its base on the ocean floor, and its 13,803-foot summit sits in conditions most visitors are not prepared for. The altitude gain from sea level to summit is roughly equivalent to the climb from Everest base camp to the top. The drop in oxygen and atmospheric pressure can cause altitude sickness, which can escalate to life-threatening High Altitude Pulmonary Edema or Cerebral Edema. The mandatory first stop is the Visitor Information Station (Hale Pōhaku) at 9,200 feet, where you must acclimate at least 30 minutes, register, and use the buddy system.
Do not travel above the Visitor Information Station if you are under 13, pregnant, intoxicated, have scuba dived in the past 24 hours, or have high blood pressure or heart or respiratory conditions. Descend immediately and seek medical attention if you experience headache, nausea, shortness of breath, impaired judgment or loss of balance.
A dependable, fully operable 4WD or AWD vehicle is required for summit travel. The eight-mile summit road climbs nearly 5,000 feet, with unpaved single-lane sections, and most rental contracts explicitly prohibit it. The summit closes to visitors 30 minutes after sunset, and winter can bring snow, ice and 100-mph winds at any time of year.
Maunakea is also sacred ground. Since the first telescope was built on the mauna in 1964, there has been ongoing conflict between Native Hawaiians and those seeking to build more observatories, most recently a proposed 30-meter telescope. In Hawaiian culture the ʻāina — the land that feeds us — is not property but kin, and Hawaiians carry a responsibility to protect and care for it.