From Glossary of Meteorology
(Or sondo, viento zonda.) A hot wind in Argentina.
The name seems to apply to two winds of quite different origin. 1) The most common use is for a dry foehn wind descending the eastern slopes of the Andes in the central Argentine in winter, probably polar maritime air warmed by descent from the crest, which is some 5500 m (18 000 ft) above sea level. It may exceed a velocity of 11 m s-1 (25 mph). Like the foehn, it sometimes begins with a high foehn (zonda de altura) that overrides a layer of cold air in the lee of the mountains, eventually sweeping it away and descending to ground level as zonda de superficie (or just "zonda"), but this initial cold air mass is not always present. The zondas carry a lot of dust in the dry season. 2) It also describes a hot, humid north wind in the pampas, in advance of a depression moving eastward, and preceding the pampero.