The Andes Mountains form the longest continental mountain range in the world, stretching approximately 8,900 kilometers (5,500 miles) along the western edge of South America. This massive range traverses seven countries—Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile, and Argentina. Due to its sheer scale and variation in elevation, the Andean climate is one of the most complex and diverse climate systems on Earth. The climate shifts dramatically over short distances, transforming from tropical rainforests at the base to permanent snowfields at the peaks.
Primary Drivers of Andean Climate Variation
The immense vertical and horizontal extent of the Andes creates three primary physical mechanisms that dictate its varied climate. The first is altitude, which governs temperature through the atmospheric lapse rate. As elevation increases, temperatures drop consistently by an average of about 6.5°C for every 1,000 meters (or 3.6°F per 1,000 feet) of ascent. This predictable cooling effect is the reason for the distinct vertical climate zones observed throughout the range.
The second mechanism is the rain shadow effect, which determines precipitation patterns. Moisture-laden air masses from the Amazon basin are forced upward when they encounter the Andean barrier. This causes the air to cool, resulting in heavy orographic precipitation on the eastern slopes and creating lush cloud forests.
After the air crests the mountains, it descends the western slopes, warming and drying out (the foehn effect). This dry air creates a dramatic rain shadow, contributing to the hyper-arid conditions found in coastal Peru and northern Chile. The third major influence is the cold Humboldt Current, which flows northward along the Pacific coast. This current cools the overlying marine air, stabilizing the atmosphere and preventing moisture from condensing into rain. This process contributes to the severe aridity of the Atacama Desert, which lies at the foot of the western Andes.
Vertical Climate Zonation
The Andean climate is traditionally classified into specific altitudinal bands, which define human settlement, agriculture, and vegetation. The lowest zone is the Tierra Caliente (Hot Land), extending from sea level up to roughly 1,000 meters (3,300 feet). This zone is characterized by consistently high temperatures, averaging between 25°C and 30°C, and high humidity, making it suitable for tropical crops like bananas, sugarcane, and cacao.
The Tierra Templada (Temperate Land) reaches up to 2,000 meters (6,600 feet). Temperatures here are moderate, ranging from 18°C to 25°C, supporting crops such as coffee and maize. This temperate environment has historically been a preferred zone for human habitation due to its comfortable conditions and agricultural productivity.
The next band is the Tierra Fría (Cold Land), located between 2,000 and 3,500 meters (6,600 and 11,500 feet), where average temperatures fall to between 10°C and 18°C. This zone is where Andean staples, such as potatoes and quinoa, are cultivated, although nighttime frosts are regular at the upper limits. Above this begins the Tierra Helada (Frozen Land), extending from 3,500 meters up to the permanent snow line.
The Tierra Helada encompasses high-altitude grasslands (páramo in the north, puna in the central Andes). Temperatures here average below 10°C, supporting only specialized cold-resistant grasses and shrubs, with livestock grazing being the main human activity. The final zone, Tierra Nevada (Snow Land), begins at the permanent snow line, where precipitation falls as snow and temperatures remain below freezing year-round. This line varies significantly by latitude, exceeding 5,000 meters in the dry, high-altitude central Andes.
Latitudinal Climate Regions
The climate of the Andes changes fundamentally from north to south, driven by the mountain range’s immense latitudinal span. The Northern Andes (Venezuela, Colombia, and Ecuador) lie close to the equator and are subject to tropical influence. This region is characterized by high humidity and consistent year-round temperatures, with seasons defined primarily by changes in rainfall rather than temperature. The vertical zones here are typically wetter, with extensive cloud forests found on the mid-slopes.
The tropical climate means that temperature variation between day and night often exceeds the variation between seasons. This consistent warmth and moisture support high biodiversity, especially in the Tierra Templada and Tierra Fría zones. The snow line in the Northern Andes is relatively high, usually between 4,500 and 4,800 meters, due to the solar radiation near the equator.
Moving southward, the Central Andes (Peru, Bolivia, and parts of northern Chile and Argentina) transition into a more arid and seasonal climate. This region is dominated by the high Altiplano plateau and the influence of the cold Humboldt Current. The climate is marked by extreme diurnal temperature ranges, where daytime warmth can quickly drop to freezing at night, particularly at high elevations.
The Central Andes experience a distinct wet season (December to March) and a prolonged dry season, making water availability a constraint on agriculture and human settlement. The aridity is so pronounced that the western flank includes the Atacama Desert, where the rain shadow and the chilling effect of the ocean current suppress virtually all precipitation.
The Southern Andes, stretching through central and southern Chile and Argentina, enter temperate and subpolar climate zones. This final section is subject to strong westerly winds from the Pacific Ocean, which deliver heavy precipitation, especially in the winter months. The climate is distinctly seasonal, with cold, wet winters and heavy snowfall, contrasting with the tropical consistency of the north. The southern Patagonian Andes feature vast ice fields and glacial landscapes, with the permanent snow line dropping progressively as the mountains near the poles. In the far south, the snow line descends to as low as 500 meters above sea level, a stark contrast to the high-altitude snow caps near the equator.