Climate

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.

The Coast

The coast is a microclimatic region. The region is affected by the cold Humboldt Current, El Niño Southern Oscillation, tropical latitude and the Andes mountain range.

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.

Northern Coast

The northern coast consits of the eastern region of Lambayeque, the Piura Region and the Tumbes Region. The northern coast has a curious tropical-dry or also called tropical-savanna climate. This region is a lot warmer and can be unbearable during summer months where rainfall is also present. The region differs from the southern ones by having presence of shrubs, equatorial-dry-forests, mangrove forests, tropical valleys near rivers such as Rio Chira or Rio Tumbes, and is blessed with clear sunny skies for most of the year. The average temperature is 25°C.

This climatical reasons for change are the presence of the warm Niño Current during the summer months (December to April), the eventual El Niño Phenomenon and the passing of Amazon Jungles clouds due to mountain openings and lower altitudes of the Andes Chain.

Summer (December through March) is humid and very hot, with average temperatures that vary from 25°C during the night to around 34°C during the day, although north of Lambayeque it can reach the 40°C. Winters (June-September) are cooler during the nights; around 16°C during the night, to around 27°C during the daytime.

The northern coast receives rainfall during the summer from convective storms that form inland or over the Gulf of Guayaquil, with annual totals as high as 400 cm, concentrated mainly between January and May.

Central and Southern Coast

The central and southern coast consists of a subtropical desert climate composed of sandy and rocky shores, occasional garúas, both foggy and sunny days exchanging places and inland cutting valleys. These regions are usually characterised by having mildy cold lows (14°C) and also mild highs (30°C). The occasional garua or fog of the central and southern is common during winter months yet even during summer days there are some foggy days.

Even though the region is located at tropical latitudes, the Humboldt Current is 7 to 8 degrees Celsius colder than normal tropical seas at 14 to 19°C. This fact affects the coastal terrain preventing high tropical temperatures from developing, and since the Andes mountains tend to be closer to the coast it also prevents Amazon clouds to appear, creating a shade effect with low annual rainfalls, varying from 30 cm at 3°S, to less than 5 cm south of 6°S. The central and southern coast receives precipitation from persistent winter drizzles that peak in August and September.

The central coast is composed of regions like La Libertad, Ancash and Lima, and has a spring-like climate for most of the year. Foggy and sunny days intermingle around the humid sand dunes most of the year.

Most summers (January-April) have pleasant temperatures from 19 to 22°C during the nights to about 29 to 30°C during daytime. Winters (June-October) are very humid, and range from 14 to 15°C during the nights to around the 17 to 18°C during the day.

The spring and autumn months have a pleasant climate that ranges from 24°C during the day to around 17°C during the night. Further inland, away from the coast and on to the yunga valleys, the climate is drier and warmer during all seasons: around 3°C warmer in any given month.

The southern coast composed of Ica, Arequipa, Moquegua and Tacna regions have a drier and warmer climate during the day-time for all months except for winters. There are regions famous for their sand dunes and impressive deserts since the climate is drier and hotter. The temperatures can go as high as 36°C in the Nazca and Ica regions inland, yet can fall to 8 or 9°C during the winter months. During the daytime temperatures rarely go below the 22 or 23°C for all months.

The Andes

The climate of the Andes exhibits the largest diversity among the country. Temperature varies 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 characterised very dry conditions and cold nights and mornings.

There is a marked southwest-northeast rainfall gradient with the driest conditions (20-50 cm/year) along the southwestern Andes, and the wettest conditions along the eastern slopes (>100 cm/year). Rainfall is also higher 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 5,000m during the rainy season, and occasionally above 3,800 m between May and August.

Below the 2,500 m mark, the temperatures vary between 5 and 15°C in the night versus 18 to 25°C in the day. Between 2,500 and 3,500 metres, the temperatures vary from 0 to 12°C in the night and from 15 to 25°C during the day. At higher elevations from 3,500 to 4,500 metres, the Puna ecoregion, the temperature varies from -10 to 8°C during the night versus 15°C during the day.

The Lowlands

The eastern portions of Peru include the Amazon Basin (or selva baja), a region that is larger in the north than in the south. Representing roughly 60% of Peru's national territory, this area includes the Amazon, Marañón, Huallaga and Ucayali Rivers. Comprised of a vast tropical forest and countless rivers and streams, the climate of this region is warm and rainy most of the year, with rainfall varying from 200 to 400 cm per year.

Temperatures range between 18-36°C most of the year, although on occasions the temperature can rise over the 42°C mark. The average temperature is 28°C.

High Amazon

The High Amazon (or selva alta) is found on the eastern slopes of the Andes. This region is one of the wettest places on earth due to the tropical effects and the falling Andes rivers. Annual rainfall ranges from 300 to 1,500 cm. The average temperature is 24°C. Temperatures are less suffocating than the Amazon Basin yet it can go over 35°C and as low as 15°C.