page_title: Climatic regions of Argentina
section_title: Northwest
hierarchical_section_title: Climatic regions of Argentina / Northwest
caption_attribution_description: English: Desert scenery near La Rioja, Argentina. December 2003.
context_page_description: Due to its vast size and range of altitudes, Argentina possesses a wide variety of climatic regions, ranging from the hot subtropical region in the north to the cold subantarctic in the far south. Lying between those is the Pampas region, featuring a mild and humid climate. Many regions have different, often contrasting, microclimates. In general, Argentina has four main climate types: warm, moderate, arid, and cold in which the relief features, and the latitudinal extent of the country, determine the different varieties within the main climate types.
  Northern parts of the country are characterized by hot, humid summers with mild, drier winters, and highly seasonal precipitation. Mesopotamia, located in northeast Argentina, has a subtropical climate with no dry season and is characterized by high temperatures and abundant rainfall because of exposure to moist easterly winds from the Atlantic Ocean throughout the year.
context_section_description: Northwest Argentina consists of the provinces of Catamarca, Jujuy, La Rioja, and western parts of Salta Province, and Tucumán Province. Although Santiago del Estero Province is part of northwest Argentina, much of the province lies in the Chaco region.
  Northwest Argentina is predominantly dry, hot, and subtropical. Owing to its rugged topography, the region is climatically diverse, depending on the altitude, temperature, and distribution of precipitation. Consequently, vegetation differs within these different climate types. In general, the climate can be divided into two main types: a cold arid or semi-arid climate at the higher altitudes, and warmer subtropical climate in the eastern parts of the region. Under the Köppen climate classification, the region has 5 different climate types: semi–arid (BS), arid (BW), temperate climate without a dry season and with a dry season (Cf and Cw respectively), and an alpine climate at the highest altitudes.
  The atmospheric circulation is controlled by the two semi–permanent South Atlantic and South Pacific highs, and the Chaco Low. During summer, the interaction between the South Atlantic High and the Chaco Low brings northeasterly and easterly winds that carry moisture to the region, particularly in the northern parts. The movement of moist air into the region during summer results in very high precipitation. Most of the precipitation comes from the east since the Andes block most moisture from the Pacific Ocean. Southern parts of the region are influenced by cold fronts travelling northward. These cold fronts are responsible for producing precipitation during summer. For example, in Tucumán Province, cold fronts are responsible for 70% of the rainfall in that province. Furthermore, the intertropical convergence zone (or doldrums) reaches the region during the summer months, leading to enhanced precipitation. During the winter months, the intertropical convergence zone, the South Pacific, and the South Atlantic highs move northward while the Chaco Low weakens, all of which results in the suppression of rain during the winter. With the Andes blocking most rain bearing clouds from the Pacific Ocean, along with atmospheric circulation patterns unfavourable for rain, this results in a dry season during winter. The Chaco Low attracts air masses from the South Pacific High, creating a dry and cold wind, particularly during winter. At the highest altitudes, westerly winds from the Pacific Ocean can penetrate during the winter months, leading to snowstorms.
caption: Arid and hot weather predominate at the lower altitudes in the Andean valleys in northwest Argentina.
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