more milder climate. At the highest elevations (over 4,000 m), icy conditions persist year round. The diurnal range is very large with very hot temperatures during the day followed by cold nights. Amongst all locations in Argentina, the region has the largest diurnal range in the country with areas in San Juan Province having a diurnal range exceeding . The Andes prevent rain–bearing clouds from the Pacific Ocean from coming in, while its latitude puts it in a band of the sub-tropical high pressure belt keeping this region dry. With very low humidity, abundant sunshine throughout the year, and a temperate climate, the region is suitable for wine production. Droughts are often frequent and prolonged. The Cuyo region is influenced by the subtropical, semi–permanent South Atlantic anticyclone to the east in the Atlantic, the semi-permanent South Pacific anticyclone to the west of the Andes, the development of a low pressure system ("Chaco low") over northern Argentina and westerlies in the southern parts of the region. Most of the precipitation falls during the summer, when hot temperatures and high insolation lead to the development of a low pressure system ("Chaco low") situated over northern Argentina that interacts with the South Atlantic anticyclone to generate a pressure gradient that brings moist easterly winds to the region, favouring precipitation, which mostly occurs in the form of convective thunderstorms. More than 85% of the annual rainfall occurs from October to March, which represents the warm season. In contrast, the winter months are dry due to these systems weakening, and the lower insolation that weakens the Chaco low over northern Argentina. Eastern and southeastern areas of the region receive more precipitation than the western areas since they receive more summer rainfall. As such, most of Mendoza province and San Juan province receive the lowest annual precipitation with mean summer precipitation averaging less than and in rare cases, no summer rainfall. Further eastwards in San Luis province, mean summer rainfall averages around and can exceed in some areas. Higher elevation locations receive precipitation in the form of snow during the winter months. In the Cuyo region, annual precipitation is highly variable from year to year and appears to follow a cycle between dry and wet years in periods of about 2, 4–5, 6–8, and 16–22 years. In wet years, easterly winds caused by the subtropical South Atlantic anticyclone are stronger, which causes more moisture towards this