With 50,000 hectares of vineyards, this is Argentina's second largest wine-growing region after Mendoza, contributing a quarter of production. The vineyards are largely located on the banks of the Rio San Juan around the provincial capital of the same name. The river also supplies much of the water for the artificial irrigation that is indispensable here. The climate is hotter than in Mendoza, with daytime temperatures of over 40 °C and only 150 millimetres of rainfall annually. Compared to Mendoza, the vineyards are also much lower, averaging 650 metres above sea level. The best areas are in the higher valleys of the Tulum, Ullun and Zonda rivers. The native varieties Cereza, Criolla Grande, Pedro Giménez and Torrontés Sanjuanino, as well as Muscat d'Alexandrie are the main grapes grown. Most of these are used to produce base wines for brandy, blended wines, sweet fortified wines, Vermouth and RCGM (concentrated grape must) are produced. Increasingly, the international grape varieties Cabernet Sauvignon, Chardonnay, Chenin Blanc, Merlot and Syrah are being pushed with a strong trend towards quality wines. Well-known producers are Bodegas y Viñedos Santiago Graffigna and Peñaflor.