A beautiful view of noctilucent clouds over a lake. These night shining clouds are tenuous cloud-like phenomena in the upper atmosphere of Earth. They consist of ice crystals and are only visible during astronomical twilight. They are most often observed during the summer months from latitudes between ±50° and ±70°. They are visible only when the observer and the lower layers of the atmosphere are in Earth's shadow, but while these very high clouds are still in sunlight.