Horse latitudes or Subtropical High are subtropic latitudes between 30 and 35 degrees both north and south. This region, under a ridge of high pressure called the subtropical high, is an area which receives little precipitation and has variable winds mixed with calm.
The term horse latitudes supposedly originates from when Spanish sailing vessels transported horses to the West Indies. Ships would often become becalmed in mid-ocean in this latitude, thus severely prolonging the voyage; the resulting water shortages would make it necessary for crews to throw their horses overboard.
The term might be derived from the "dead horse" ritual, a practice in which the seaman would parade a straw-stuffed effigy of a horse around the deck before throwing it overboard. Seamen were often paid partly in advance before a long voyage (see Beating a dead horse), and the "dead horse" was this period of time (usually a month or two). The ceremony was to celebrate having worked off the "dead horse" debt. As European west bound shipping would reach the subtropics at about the time the "dead horse" was worked off, the region became associated with the ceremony.
The consistently warm, dry conditions of the horse latitudes also contribute to the existence of temperate deserts, such as the Sahara Desert in Africa, the southwestern United States and northern Mexico, and parts of the Middle East in the Northern Hemisphere, and the Atacama Desert, the Kalahari Desert, and the Australian Desert in the Southern Hemisphere.