Glowing silver-blue clouds – called noctilucent or night shining clouds – sometimes light up summer night skies. They’re seen at high latitudes – say, about 45 degrees N. or S. – from May through August in the Northern Hemisphere and from November through February in the Southern Hemisphere. In 2015, the northern noctilucent cloud season has already begun.
I used this idea in my futuristic Intervenus Series– a little truth goes a long way in Science Fiction. Venus is a planet that rotates once during her year around the sun. Half of the Venus year is dark, and half light. In my series Venus is habitable after a great asteroid impact which forced planets outward. Earth sunk into a second ice age. Meteors caused underground water to erupt on Mars and Venus, creating breathable atmospheres.