Cirrus and cirrocumulus clouds at sunset. Cirrus clouds are elongated tufted clouds that are found at altitudes over 5000 metres. They consist of tiny ice crystals which are blown by the wind into wispy shapes. This variety, cirrus spissatus, is a dense cirrus found high up into the stratosphere, as high as altitudes of over 13,000 metres. Cirrocumulus clouds usually occur at an altitude of 5 to 12 kilometres, and are patchy sheets with ripples or tufts. Photographed at sunset in September over southern England.