Mauna Kea
At 13,796 feet, Mauna Kea is one of the world's premier astronomical sites — the Milky Way looks painted on. Two very different experiences: (1) The Visitor Information Station (VIS) at 9,200ft — free, no 4WD required, open nightly 6–10pm, telescopes available. VIS staff run a free public stargazing evening with larger telescopes once a month (reservation required; check ifa.hawaii.edu/vis). This is excellent for anyone without a 4WD vehicle. (2) Summit at 13,796ft — requires a 4WD vehicle above the VIS; rental cars are neither permitted nor insured on the unpaved summit road. Mandatory: acclimatize 30+ minutes at the VIS before going higher. No children under 13 above 13,000ft recommended. Temperature at summit: 30–45°F with extreme wind chill regardless of the coast forecast.
Self-drive: 4WD required above the VIS at 9,200ft — standard rental cars cannot go to the summit. Free public stargazing at VIS nightly 6–10pm. Guided tours to the summit: Hawaii Forest & Trail or Mauna Kea Summit Adventures from $200/person (include 4WD transport, warm gear, and expert guide). Book guided tours 1–2 weeks ahead.
Summit weather can change rapidly. Evening temperature at summit: 30–45°F with extreme wind chill. Tours cancelled if cloud ceiling drops below the summit.