Noctilucent clouds in Lithuania

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‘Night shining’ clouds. Noctilucent clouds

It’s around this time of year when some lucky people get to witness these beautiful rare clouds. Known as noctilucent - or ‘night shining’ - clouds, they’re the highest clouds in our sky and only visible during summer. They’re made up of icy dust glowing at the edge of space, roughly 50 miles above the Earth’s surface. The trick to seeing them is to gaze up into the sky at twilight, when the sun has dipped below the horizon but the high-altitude noctilucent cloud is still in sunlight. These clouds occur at latitudes of between roughly 50° and 70° in the Northern Hemisphere and equivalent latitudes in the Southern Hemisphere.

Generally light blue or silver, noctilucent clouds are distinct in their patterns of streaks, waves and whirls. It’s not fully understood what causes them, although some recent studies suggest methane levels could contribute to atmospheric water vapour that rises high into the layer of atmosphere known as the Mesosphere, where they form. They were first observed in 1885, making them the newest type of cloud.