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Medium clouds are found from between 6,500 and 23,000 feet (2,000 to 7,000 meters) and include (from highest to lowest) altocumulus, altostratus, and nimbostratus. Altocumulus clouds are rounded puffs of cloud larger than cirrocumulus. Altostratus clouds cover the sky with a greyish veil through which the sun or moon may shine as a spot of pale light. Nimbostratus clouds are thick, dark, and shapeless and usually bring rain or snow.