Looking out of my window, just before sunset, I saw the biggest and longest "green flash" just before the sun went down.
The green flash is a phenomenon that occurs at sunset and sunrise when conditions are favorable, and results when two optical phenomena combine: a mirage and the dispersion of sunlight. As the sun dips below the horizon the light is being dispersed through the earth's atmosphere like a prism.
The green flash is an incredibly rare sight no matter where you are, notorious for its unpredictability. Green flashes can occur at sunrise but are more common at sunset. On land, the best chance of seeing a green flash will come from a place of elevation, with a clear view of the horizon.