The Shining

If you happen to be out in the early hours and have clear skies and a prospect of the N. Eastern horizon, keep and eye open for Noctilucent Cloud. I took this photo on Saturday morning, at around 03:15, of a display which lasted from sometime after 02:00 until around 03:45. The street lights are those of the centre of Merthyr.

Noctilucent Cloud over Merthyr

Noctilucent Cloud isn't normal cloud. It forms so high up in the atmosphere (around 83km) that it is classed as space weather, as are aurora. The tiny ice crystals from which they are made are formed but moist air lifted up to the edge of space by summer air currents and form around particles of soot left over from the burning up of meteors.
They are so diffuse that they cannot be seen in day time, but are so high that when the sun is 6 to 16 degrees below the horizon, it can still illuminate them, causing them to glow a ghostly pale blue in the dark sky, always in the northern quarter. They only occur in the summer months and July is the best month in which to see them.