Peruvian Andes: Sierra Natural Region (Peru)
The Peruvian Andes, part of the greater Andes system of South America, are formed by three main cordilleras that traverse the entire country. The Sierra natural region features fertile river valleys, high plains, deep canyons and the Altiplano plateau.
Peruvian Andes
The Peruvian Andes are integral to Peru's Natural and Geographic Landscape. A part of the greater Andes mountain system of South America, it is formed by three ranges of mountains with fertile river valleys, high plains and deep canyons. Much of the Peruvian Andes is considered part of the Tropical Andes, a climate-delineated region.
Sierra Natural Region
La Sierra is the highlands natural region of the Peruvian Andes. It includes the Altiplano plateau as well as the highest peak of the country, the 6,768 m (22,205 ft) Huascarán.
The Peruvian Andes traditionally have been organized into three major mountain ranges (cordilleras), which come together at the Vilcanota, Pasco and Loja (Ecuador) knots.
The high average altitude of the three main mountain ranges or cordilleras and regional and local climatic conditions have resulted in the extensive development of glaciers in many places.
The highest secondary mountain groups are the Cordillera Blanca, Huayhuash, Ampato, Vilcanota and Vilcabamba.

Map of Peru and its Cordilleras
Cordillera Occidental
The Cordillera Occidental constitutes the western branch of the Peruvian Andes. It extends in a northwest-southeast direction from the Ecuadorian border to the Chilean border. Its western limits border the coastal pampas of the Pacific Ocean. It is approximately 2,000 km (1,242 mi) long and 250 km (155 m) wide.
Mountain groups within the Cordillera Occidental of Peru:
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Cordillera Ampatga
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Cordillera Volcánica
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Cordillera Yauvos
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Cordillera Barroso
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Cordillera Raura
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Cordillera Chila
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Cordillera Huallanca
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Cordillera Huanzo
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Cordillera La Viuda
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Cordillera Chonta
Cordillera Central
The Cordillera Central is the central range of the Peruvian Andes that extends from the Cóndor mountain range on the border with Ecuador in the north to the Vilcanota knot in the south, passing through the Pasco knot in central Peru. It is approximately 1,500 km (932 mi) long and is less elevated than the Cordillera Occidental, except in its southern sector.
Mountain ranges within the Cordillera Central of Peru:
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Cordillera Huaytapallana
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Cordillera La Raya
Cordillera Oriental
The Cordillera Oriental is a mountainous alignment that constitutes the eastern branch of the Peruvian Andes. It traverses the entire country, from the Ecuadorian border in the north to the Bolivian border in the south. It has an approximate length of 1,800 km (1,118 mi) and is located on the border with the Amazon Rainforest region.
Mountain ranges within the Cordillera Oriental of Peru:
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Cordillera Apolobamba
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Cordillera Urubamba
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Cordillera Carabaya
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Cordillera Huaguruncho
Climate
The Andes shelter the widest variety of climates in the country. The weather is semi-arid in the valleys, moist in higher elevations, and towards the eastern flanks.
The western slopes are arid to semi-arid and receive rainfall only between January and March. Below the 2,500 m (8,200 ft) mark, the temperatures vary between 5 and 15 °C (41 and 59 °F) at night versus 18 to 25 °C (64.4 to 77.0 °F) during the day.
Between 2,500 and 3,500 m (8,200 and 11,500 ft), the temperatures vary from 0 to 12 °C (32.0 to 53.6 °F) at night and from 15 to 25 °C (59 to 77 °F) during the day.
At higher elevations from 3,500 to 4,500 m (11,500 to 14,700 ft), the Puna ecoregion, the temperature varies from −10 to 8 °C (14.0 to 46.4 °F) during the night versus 15 °C (59 °F) during the day.
The northernmost regions of the Andes around Cajamarca and Piura regions have Páramo climates.

Altitude map of Peru