WHEN: All month, times as specified
Noctilucent cloud (NLC) season typically runs from late May through to early August, with June and July being the months most likely to deliver a display. Noctilucent or ‘nightshining’ clouds are the highest clouds on the planet, formed in the mesosphere, in a narrow layer 76-85km up. One of the prime seeding agents for their formation is the fine dust left behind after a meteor vaporises in the atmosphere.
Their appearance is not guaranteed and spotting them can be tricky at UK latitudes. There’s no guarantee that they will be present on any given date and even if they are, you’ll need good clear skies, a low horizon and to be looking at the right time. They appear to shine at night because even when the Sun is below the horizon from the ground, from their altitude they can still ‘see’ it above the horizon. Sunlight reflects off them and they appear bright against the deep twilight summer night sky.
Look for them low down in a northwest direction 90-120 minutes after sunset, or a similar time low down in the northeast before sunrise. The reason they appear in these directions at these times is because the brightest reflections occur directly above the Sun’s position below the horizon. If a really extensive display occurs, it’s possible to watch it spread from the northwest, through north and through to the northeast as it tracks the Sun’s position.
A few years ago, NLC displays were widely reported from the UK and it became something of a regular activity to report and photograph them. Over recent years the displays have been less common, but it’s always worth keeping an eye out. If they are there, they typically appear with an electric blue colour, often displaying a fine network of rippling patterns.
Direction and timing are critical to seeing NLCs; a flat horizon is also highly recommended