Honolulu, HI UV Index Today

Honolulu is the only state capital inside the tropics, at 21.3 degrees north, and the consequence is visible twice a year. The subsolar point crosses the island in late May and again in mid-July, putting the sun exactly overhead near midday. Bishop Museum named the event Lāhainā Noon and publishes the timing island by island. Vertical objects lose their shadows entirely for a few minutes. On those two dates sunlight takes the shortest path through the atmosphere it ever takes over American ground.

Hawaiʻi keeps no daylight saving, and the city sits nearly eight degrees west of the 150th meridian its clocks run on, so solar noon holds near half past twelve all year round. The peak hour barely wanders across the calendar. At the December solstice the midday sun here still stands about 45 degrees up, higher than Chicago’s noon sun manages for roughly five months of its year.

Cloud is the local variable, and terrain decides it. The northeast trades pile orographic cloud against the windward wall of the Koʻolau Range and drop their rain there. Honolulu sits on the leeward south shore, where that same air descends and dries out. Waikīkī can hold full sun while Kāneʻohe, a few miles across the ridge, sits under overcast. Between those two May and July dates the sun’s declination exceeds the city’s latitude, so for about seven weeks the noon sun sits in the northern half of the sky and a north-facing wall takes direct light at midday, which never happens on the mainland.