The Argentine Northwest is a geographic and historical region of Argentina composed of the provinces of Catamarca, Jujuy, La Rioja, Salta, Santiago del Estero and Tucumán.
The Argentine Northwest comprises very distinct biomes, or geographical and climatic regions.
Besides the Yungas jungle on the eastern fringe of the region, the only fertile lands are those near the river basins, which have been irrigated extensively. Across millenia the erosive forces of these rivers has gradually created a multitude of red-rock canyons, such as the Quebrada de Humahuaca and the Valles Calchaquíes.
West of these valleys the peaks of the Andes reach heights of over 6,000 metres (20,000 ft) and the Altiplano, an extensive 3,500-meter high plateau, dominates the landscape and continues far north into Bolivia and Southern Peru.
As moist easterly winds reach the sub-Andean Sierras and the eastern slopes of the Andes, they drop much of their moisture. As a result, these areas--such as the Yungas jungle mentioned above--are characterized by a warm sub-tropical climate with abundant rain.
The now dry winds then continue their path to the west, leaving the Puna and the arid Steppe with wide temperature differences. This latter climate pattern is common in much of the region.
Precipitation in the Argentine northwest follows a summer monsoon pattern, with most of the 700 millimetres (28 in) of annual rainfall falling in the austral summer from December to March.