Due to the effect of the cold Humboldt current in the Pacific ocean and the presence of the Andes to the east, the coast from Ecuador to Chile is mostly barren. The southern region is part of the Atacama desert, the driest spot on the planet. In Lima from May through September, the city experiences what is known as the garúa, a thick layer of cloud which blankets the city accompanied by drizzle and very low temperatures. Once out of Lima the weather changes drastically. Up to the Ecuadorian border and down to Chile, the sun shines bright and temperatures often top 30ºC. October to May is Summer. Lima becomes hot and humid while everywhere else on the coast suffers from a relentless sun that shows no mercy.
The mountains have two seasons: dry and wet. From May to October rain is sporadic and sunshine fills the sky daily. During the months of November through April, rainfall is heavy and temperatures plunge drastically once the sun sets.
Peru Information - Weather
The jungle is divided into the cloud forest (above 700m) and lowland jungle (below 700m). The cloud forest features a subtropical, balmy climate, with heavy rainfall between November and March, and sunshine from April to October. It is always cool at night.
The lowland jungle regions experience two extremely different seasons, which accentuate depending on its proximity to the equator. The dry season from April to October is marked by sunshine-filled days and high temperatures, often over 35ºC. During these months, the water level of the rivers drops and roads are in decent shape. The rainy season, however, which runs from November to March, features frequent downpours (at least once a day), and muddy roads which make traveling difficult to impossible.
Humidity is high in all jungle regions throughout the year. In the north the jungle is hot all year round whereas in the south the jungle is sometimes hit by cold winds, known locally as a friaje, a front that moves north from the far south of the continent between May and August, when temperatures plunge to 8-12ºC.