Clouds at different heights

Low-level cloud: Nimbostratus, stratus, cumulus, stratocumulus, up to 6,500ft (2,000m). Medium-level cloud: Altocumulus and altostratus, between 6,500-23,000ft (2,000-7,000m).

High-level cloud: Cirrus, cirrocumulus, cirrostratus and cumulonimbus, which can extend through all three levels. Above 23,000ft (7,000m).