Chile has a remarkable shape. It extends over 4,600 km/2,850 mi, between 18° and 56°S, on the Pacific coast of South America, yet has an average breadth of only 180 km/112 mi. Its northeastern border with Bolivia and eastern border with Argentina follow the crest-line of the main Andes mountain chain, so that the eastern part of this narrow country is very mountainous with the higher parts rising to over 6,500 m/21,300 ft. It is bordered by Peru on the northwest. South of Santiago the mountains are lower and more broken, but the country is rugged with hundreds of small islands offshore from Puerto Montt to Tierra del Fuego.
Much of Chile, therefore, has a mountain climate with perpetual snow and glaciers in the higher parts. The height of the snowline gradually decreases from north to south as temperature decreases and precipitation increases. Precipitation is light on the mountains in northern Chile, so the snowline is high.
Most people live in the lowlands of central Chile between Valparaíso and Valdivia. The north of the country is a desert and the southern third is rugged and densely forested, and has a changeable, cool, wet climate.
The lowlands of northern Chile, from the border with Peru southwards to about Coquimbo at 30°S, is one of the driest regions in the world. This is a typical 'cold-water-coast desert' where, in spite of being virtually rainless, the weather is often cloudy and relatively cool for the latitude. The coastal strip has much fog and frequent light drizzle with rather low amounts of sunshine. The cloud usually breaks up by day inland in summer and temperatures here are a little higher.
There is a small difference of temperature from summer to winter and the weather is remarkably constant from one day to another. The table for Antofagasta illustrates conditions in this coastal desert.
Central Chile, between about 32° and 38°S, has a Mediterranean type of climate. Summers are virtually rainless and quite warm, while the winter months from April to September are mild and moderately wet with changeable weather. Frost and snow occasionally occur inland but are rare on the coast. Daily hours of sunshine on the coast average from two to three in winter to eight or nine in summer. Inland, where there is less cloud, this increases to three to four in winter and nine to ten in summer. The table for Santiago is typical of this central portion of Chile.
Southern Chile, from about 38°S, is the third climatic region. The table for Valdivia is representative of the north of this area while that for Punta Arenas, on the Strait of Magellan, is representative of the extreme south of the country. Much of this area is very wet all the year round with much cloud and frequent disturbed, changeable weather. Annual precipitation is 2,500-5,000 mm/100-200 in, much of which falls as snow on the higher mountains and farther south.
Winters are rarely very cold on the coast but the summers are cool and cloudy. The weather and climate here are very similar to that on the coasts of British Columbia, Alaska, or Norway. Punta Arenas is exceptional in having a very low annual rainfall because it is sheltered from the wet, westerly winds by the southern Andes. The weather and climate here are similar to that of southern Argentina.
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