My parents were just on a trip to Hawaii and claimed they saw a rainbow at night. Is that possible?
It is absolutely possible. Lunar rainbows or moonbows are common in the tropics, but are rather rare at mid and high latitudes. They form in the same manner as a common rainbow, except the light source is the moon rather than the sun, with moonlight reflected and refracted through raindrops to form a pale-colored bow. Since moonlight is much dimmer than sunlight, the moonbow’s colors are faint and muted in comparison with a typical rainbow, often appearing in varying shades of gray and white .Many moonbow reports originate from Hawaii and other tropical locales, where the co-existence of nocturnal showers and moonlight is much more common than at higher latitudes, where night skies tend to be overcast when it is raining.