??????????? ??????, also known as night-shining clouds, are hazy cloud-like formations that occur in Earth's upper atmosphere. They are made up of ice crystals that can only be seen in the astronomical twilight. They are most frequently seen between the latitudes of 50° and 70° during the summer months. They are only observable during the summer months in the local area, when the Sun is below the observer's horizon but the very high clouds are still in sunlight.