The chilean climate is strongly influenced by its two mayor geographic barriers, the Andes cordillera that follows the western border of the country and the Pacific ocean to the east. There are three different climatic regions. The north of the country is an extremely dry desert with almost no precipitation throughout the year. South of 30S there is a transition zone to a winter rain climate, which is the only rainfall regime in the country. The intensity and amount of rainfall increase with latitude until about 42S where from rainfall is more evenly distributed throughout the year.

The Arid North

The Copiapo river (27S) marks the southern border of an extreme arid desert that dominates most of the region west of the Andes from the Ecuador/Peru border. The region is isolated by the Andes of any moisture coming from the Amazon, that only sometimes reaches the Chilean and Bolivian Altiplano during the summer months (Jan-March), these winds are consequence of the Bolivian high that establishes itself aver Bolivia strongly during the summer months. South of Copiapo and to about 31S the region is still dry, but occasional polar front reach the region during the winter so that annual rainfall gradually reaches about 500 mm per year. The temperature variations in the north of Chile are very small, with an annual range of less than 7C. Stratus clouds are very common during winter at the coast and about half of the time during summer.

Central Chile

Between 30 and 42S winds become increasingly more westerly and with it more frequent more intense precipitation is found with increasing latitude, this region is denominated Central Chile. During winter the south Pacific anticyclone is in its southernmost position and migrates northwards during the winter allowing cold fronts to reach the coast of Chile bringing rainfall. The Bio-Bio river (37S) marks the southern border  of the pure winter rainfall season. South of this river summer rains start to be more important, so that in the southern central part summer rains contribute to about 20% to the total annual rainfall. The temperature decreases with latitude and altitude and the annual range increases especially in the central valley away from the coast.

Southern Chile

The extreme southern part of Chile is under the influence of strong westerly flow all year long, so that rainfall is found all year long. Temperature range of diurnal means and annual means are small and low.
 
 
 
 

Region	Rainy season	Dry season
North	No rainy season	All year long
Altiplano	Jan-Mar	Apr-Dec
Central Chile	Jun-Aug	Dec-Feb
Southern Chile	All year long	No real dry season, less rain during Dec-Feb