Noctilucent clouds in Denmark
© Adrien Mauduit
Time-lapse video of the amazing noctilucent cloud display over northern Europe on July 12-14, 2016. Adrien Mauduit called it a "storm" of these clouds

Adrien Mauduit in Denmark posted this video of last week's fantastic display of noctilucent clouds - sometimes called night-shining clouds - to EarthSky Facebook. He wrote:
On the nights of the 12-13 and 13-14 of July, 2016, Denmark has witnessed two very powerful and bright noctilucent cloud shows in a row. The brightest and broadest I can remember to date anyway.
Noctilucent clouds are a beautiful seasonal phenomenon. The clouds appear at night and shine silver-blue. They sometimes light up summer night skies 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. These clouds form in the highest reaches of the atmosphere - the mesosphere - as much as 50 miles (80 km) above the Earth's surface. You can see in the video above that ordinary clouds are scuttling below them ...

Noctilucent clouds are thought to be made of ice crystals that form on fine dust particles from meteors. They can only form when temperatures are incredibly low and when there's water available to form ice crystals.

Thank you, Adrien!