Climate of Peru

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The climate of Peru is very diverse. The north-south extension of the country and the presence of the Andes mountains together produce a large variety of climates and microclimates. In general, the climate on the coast is subtropical and the region receives very little rainfall. The Andes mountains observe a cool climate with rainy summers and very dry winters. The eastern lowlands are warm and rainy with a short dry season from June through August.

[edit] The coast

The climate of the coast ranges from warm-semiarid north of 5°S to cool-arid south of 8°S. Despite of the low latitude (3°S-18°S), the entire coastal region has a marked annual temperature cycle in response to the direct effects of the sea surface temperature. The warmest period occurs from January through March and the coolest period from July through September. North of 6°S summer (winter) maximum temperatures range from 28-37°C (23-30°C), and minimum temperatures range from 20-24°C (14-18°C), with larger differences away from the coastline. Inland locations south of 6°C are exposed to summer (winter) maximum temperatures of 26-35°C (20-26°C) and minimum temperatures of 15-21°C (7-12°C). Coastal locations south of 6°S are exposed to summer (winter) maximum temperatures of 24-29°C (16-21°C) and minimum temperatures of 18-22°C (12-15°C). Rainfall is scarce and varies from 300 mm at 3°S, to less than 50 mm south of 6°S. The northern coast receives rainfall during the summer from convective storms that form inland or over the Gulf of Guayaquil. The central and southern coast receives precipitation from persistent winter drizzles that peak in August and September. During strong El Niño events the northern coast can receive annual totals as large as 4000 mm, concentrated mainly between January and May.

[edit] The Andes

The climate of the Andes exhibits the largest diversity among the country. Temperature is an inverse function of altitude varying from temperate (annual average of 18°C) in the low-lying valleys to frigid (annual average below 0°C) in the highest elevations. Precipitation varies in different scales and has a marked seasonality. The rainy season starts in September but peaks between January and March, whereas the May-August period is characterized by strong insolation, very dry conditions and cold nights and mornings. There is a marked southwest-northeast rainfall gradient with the driest conditions (200-500 mm/year) along the southwestern Andes, and the wettest conditions along the eastern slopes (>1000 mm/year). Upon the interaction between the topography and the mean flow, some regions immediately of the Andes can receive as much as 10000 mm/year. Rainfall is also larger over mountain ranges than over valley floors, since most of the rainfall occurs in the form of afternoon convective storms during the rainy season. Lakes also modulate the distribution and rainfall amounts. Lake Titicaca, for example, induces nocturnal convective storms that produce twice as much rainfall over the lake than over the surrounding terrain. Occasionally thunderstorms can be accompanied by frequent cloud to ground lightning, strong winds and damaging hail, especially during the onset of the rainy season and over higher elevations. Snowfall is frequent above 5000 during the rainy season, and occasional above 3800 m between May and August.

[edit] The lowlands

The eastern lowlands are characterized by the Amazon Rainforest. The climate of this region is warm and rainy most of the year. Temperatures oscillate between 18-36°C most of the year and rainfall varies between 1000 and 4000 mm per year. South of 8°S, a short dry season occurs between June and August. Occasional cold surges that originate over Argentina may lower the temperature to 10-15°C. These events occur 1-5 times per year between May and September.