Driving out to the east side of Honolulu, on the climb up to the Hanauma Bay entrance, there is a viewing area out over Hawaii Kai. The day we drove that way it was showering intermittently, and at the time we got to the viewing area there was a full arc rainbow over the town below – and lots of people in the viewing area taking pictures of it.

Apart from the rainbows printed on the Hawaiian license plates, I think that this was the only one I have seen out there in all three visits to the islands.