The Argentine Northwest (Noroeste Argentino) is a geographic and historical region of Argentina composed of the provinces of Catamarca, Jujuy, La Rioja, Salta, Santiago del Estero and Tucumán.

From west to east they are: 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 millennia 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 Bolive and Southern Peru.

In February 2021, archaeologists from the University of Buenos Aires–National Scientific and Technical Research Council announced the discovery of 12 graves dated to 6,000-1,300 years ago.

[8][9] During summer, the interaction between the South Atlantic high and the Chaco low causes the low-pressure system to bring northeasterly and easterly winds that carry moisture to the region, particularly in the northern parts.

[7]: 18  In contrast, during the winter months, the Chaco low attracts air masses from the South Pacific high, creating a dry and cold wind.

[9] The Intertropical Convergence Zone reaches the region during the summer months, leading to low pressure, and unstable air masses due to the relatively high land temperatures compared to the sea during this season.

[10][6][7]: 20 [11] At the highest elevations, westerly winds from the Pacific Ocean can penetrate during the winter months, leading to snowstorms.

[13][14] Valleys in the southern parts of the region are drier than northern valleys due to the mountains on the eastern slopes of both the Andes and the Sierras Pampeanas being taller than the ones in the north (ranging from 3,000 to 6,900 m (9,800 to 22,600 ft)), presenting a significant orographic barrier that blocks moist winds from the Atlantic and Pacific oceans.

[7]: 22–23 [15]: 28  These valleys often receive less than 200 mm (7.9 in) of precipitation per year and are characterized by sparse vegetation adapted to the arid climate.

[20][21] Owing to the low precipitation in conjunction with the extreme climatic conditions, the Puna region has a water deficit in all months of the year.

[5] Snowfall is rare, averaging less than 5 days of snow per year since most of the precipitation falls in the summer in the form of rain.

[9][11][23] During an El Niño year, the westerly flow is strengthened while moisture content from the east is reduced, resulting in a drier rainy season.

[11][23] In contrast, during a La Niña year, there is enhanced easterly moisture transport, resulting in a more intense rainy season.

[18]: 11  In both the Quebrada de Humahuaca and Calchaqui valleys, winters are cold with frosts that can occur between March and September.

[21] The diurnal range is large with a thermal amplitude that can exceed 40 °C (104.0 °F) due to the low humidity and the intense sunlight throughout the year.

The Argentine Northwest is a popular destination for both domestic and international travelers, attracting neighboring Argentinos and vacationing Europeans alike.

It is heavily influenced by Spanish, Quechua and Qulla cultures, and the region is quite distinct from the rest of Argentina which is predominantly European.