Land and Resources, Climate
cordilleras, climate of Peru, Celsius degrees, ice fields, Fahrenheit degrees
The climate of Peru varies widely, ranging from tropical in the montana to arctic in the highest mountains of the Andes. Average temperatures decrease about 1.7 Celsius degrees (about 3 Fahrenheit degrees) with every 450-m (1,500-ft) increase in elevation. Permanent snow and ice fields cover peaks more than 5,000 m (16,500 ft) above sea level, and the highest elevation at which the land is suitable for agriculture is about 4,400 m (14,500 ft).
In the coastal plain the temperature is normally equable, averaging about 20°C (about 68°F) throughout the year. The coastal climate is moderated by winds blowing from the cool offshore current known as the Peru, or Humboldt, Current. The coast receives less than 50 mm (2 in) of precipitation each year, largely because the cordilleras receive most of the rain carried by the trade winds from the east. Mist-laden clouds known as garua shroud many of the slopes of the sierra from June to October, providing enough moisture to support grasslands.
In the sierra the temperature ranges seasonally from about -7° to 21°C (about 20° to 70°F). Rainfall is usually scanty, but in some localities heavy rains fall from October to April. In Cuzco, in the southeastern sierra, annual rainfall averages some 815 mm (32 in). The exposed eastern slopes of the Andes receive more than 2,500 mm (100 in) of rain annually, but sheltered locations receive much less. Rainfall amounts diminish rapidly southward, causing many changes in the vegetation.
The montana region is extremely hot and humid, although at higher elevations it is less so. The prevailing easterly winds blowing across that region gather moisture that is later deposited on the eastern Andean slopes. Annual rainfall in some districts averages as much as 3,810 mm (150 in). Most of this rain, which principally falls from November through April, eventually drains back to the montana.
Peru’s climate periodically experiences a weather pattern known as El Nino. El Nino occurs every three to seven years when unusually warm ocean conditions appear along the western coast. During El Nino the wet weather conditions normally present in the western Pacific move to the east, bringing heavy rains that can cause extensive flooding.
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