The zonda is a hot, dry, and dusty wind that descends the eastern slopes of the Andes in Argentina, primarily affecting the provinces of San Juan, Mendoza, and San Luis. It is the South American equivalent of the Alpine Fohn effect and the North American chinook: moist Pacific air rises, dumps its moisture as precipitation on the Chilean side, and descends parched and superheated down the Argentine slope.
Characteristics and impact
The zonda can raise temperatures 15-25 °C in a few hours, reaching above 40 °C even in winter, while relative humidity drops below 10 %. Wind gusts reach 80-120 km/h, lifting dust clouds that reduce visibility. It occurs between May and November (austral autumn to spring), averaging 5-10 episodes per year.
Its effects are wide-ranging: extreme wildfire risk from the combination of heat, dryness, and wind; damage to vineyards and orchards in the Cuyo wine region; respiratory and cardiovascular problems; and a documented psychological impact (irritability, insomnia, headaches) similar to the European Fohn.
The name comes from the Quebrada de Zonda in San Juan province, where the wind is felt with particular intensity. Argentine weather services issue specific zonda warnings when synoptic conditions favour these episodes. See also: chinook, Fohn effect.