Arequipa Geography & Climate

Arequipa region runs from the Pacific to the high Andes in under 200 kilometres, and volcanism shapes almost all of it.

The volcanoes

The city sits at about 2,335 metres beneath a line of stratovolcanoes: El Misti at 5,822 metres, an almost perfect cone and still active; Chachani at 6,057; and Pichu Pichu. Further out, Sabancaya erupts more or less continuously and Ampato held the frozen Inca burials. The sillar the city is built from is welded volcanic ash from these eruptions, quarried nearby, soft enough to saw and carve and hardening on exposure.

Colca canyon

The Colca river has cut a gorge more than 3,200 metres deep — roughly twice the depth of the Grand Canyon, though far narrower and less sheer — between the peaks of Ampato and Hualca Hualca. The neighbouring Cotahuasi canyon is deeper still. Both are farmed in terraces that predate the Inca.

The desert

The coastal strip is part of the Atacama system and is among the driest places on earth, crossed by a handful of rivers that support irrigated valleys and nothing in between.

The puna

Above 4,000 metres, a cold grassland of vicuna, lagoons and salt flats, including the Salinas y Aguada Blanca reserve with its flamingos.

Water from the mountains

The city and the irrigated desert valleys below it depend entirely on snowmelt and highland rainfall channelled down the Chili river and, since the 1970s, on the Majes diversion scheme that carries water from the highlands to turn desert into farmland. The whole settlement pattern of the region is a map of where water can be delivered, and nothing grows between those threads.

Earthquakes

The subduction zone offshore makes this one of the most seismically active parts of Peru, and Arequipa has been rebuilt repeatedly.

Arequipa has one of the most agreeable climates in Peru and an unusual amount of sun.

The city

At 2,335 metres in a desert, the city runs roughly 10 to 23°C year round with very little seasonal variation. Humidity is low, the sky is clear on around 300 days a year, and nights are cool. It is comfortable in any month, which is why it has a long history as a place people were sent to recover.

Rain

Almost all of the annual rainfall — only around 100 millimetres — falls in short afternoon storms between January and March. The rest of the year is effectively dry.

Altitude and sun

The ultraviolet index here is among the highest recorded anywhere, a consequence of altitude, latitude and clear air. Burning happens quickly and in cool conditions; a hat and high-factor sunscreen are not optional.

The canyon

Chivay at 3,600 metres is markedly colder, with nights below freezing from May to August, while the canyon floor a thousand metres lower is warm during the day. The daily swing is large everywhere in the highlands.

The coast

The desert strip is cool, grey and almost rainless, under the influence of the Humboldt current.

A climate people were sent to

The combination of altitude, dryness and constant sun gave Arequipa a nineteenth- and twentieth-century reputation as a place to recover from respiratory illness, and sanatoria operated here. The same qualities make it unusually pleasant to spend time in: there is no season to avoid, and the difference between January and July is a matter of a few degrees and some afternoon cloud.

Practical effect

Layers, sun protection and a warm jacket for the canyon nights, in any month.