The continent of South America is a very extensive continent in the North-South direction. Its northern most part the Gulf of Venezuela is at about 10 degrees north while the southern most tip Cape Horn is almost at about 55 degrees south of equator. As we know that chief factor affecting the climate of a place is the latitude so we can expect a wide variation in the climate of South America. Interestingly it is not so. The reason being that this continent has a conic shape and it becomes narrower and narrower as we go towards the southern latitudes and due to the combined influence of the Atlantic and the Pacific oceans, extreme variations in the temperatures are not present.
The climate of South America can be divided into the following seven climatic zones.
This climate is found in the Central Brazil, Eastern Peru and South Eastern Columbia. The temperature remains high ( around 80 F or 27 C ) throughout the year. The rainfall is heavy; usually greater than 80 inches ( 2000 mm) and is uniform all the year round and humidity is excessive. There is no winter month. No month is below 70 F (21 C ) and the range between the hottest and coolest month is very narrow. These areas lie about 7 degrees south and north of the equator. At Iquitos in Peru for example which is located at 4 degrees south and 73 W, the total annual rainfall is 103 inches ( 2600 mm) equally distributed in all months and no month receives less than 7 inches (175 mm). To give you an idea of the heaviness of rainfall compare it with London which has a total annual rainfall of 23 inches ( 600 mm ). At Iquitos the hottest month has a temperature of 78 F ( 26 C ) and coolest of 74 ( 23 C ); a range of only 4 F. Such a high temperature and abundant rainfall is responsible for one of the thickest forests in the world which are found every where in this area. The weather for the foreigner is however trying for the high humidity combined with high temperature makes the weather quite oppressive.
This type of weather is found in Northern and Southern Brazil, almost whole of Columbia, greater part of Venezuela, Guyana, Surinam and French Guiana. The rainfall is nether so heavy nor uniformly distributed among all months.. There is a definite wet and dry season. The temperature range is also greater than that of the tropical regions. Rio de Janeiro in South Eastern Brazil is the best example of this type of Climate. The total annual rainfall for this station is 44 inches (1100 mm ) which is not meager but four months from June to September each have less than 3 inches ( 75 mm ) of rainfall while March and December record more than 5 inches ( 125 m ). The coolest month is June with a temperature of 68 F ( 20 C ) and the hottest January with a temperature of 78 F ( 26 C ) showing a range of 10. It may come to the reader as a surprise that Jan. is hottest at Rio but remember that we are in the southern hemisphere where the seasons are reversed. The climate on the whole is less oppressive than that of the tropical one.
This type of climate is found in Argentina, Uruguay and Paraguay. The characteristic features are warm summers and mild winters. Rainfall is moderate and is uniform throughout the year. The range between the hottest and coldest month is much greater than that of the two regions described above. At Buenos Aires in Argentina the total Annual Rainfall is 37 inches ( about 900 mm ) equally distributed in all months so that no month is below 2.5 inch ( 50 mm). The hottest month is Jan. with a temperature of 74 F ( 23 C ) and the coolest is July with 49 F ( 9 C ); thus having a range of 35 F. There are no extremes of temperatures in this type of climate and has been ideal for foreign settlement.. This is the reason that almost 90 percent of the population of Argentina is of European origin.
Cool- Temperate Climate
These climatic conditions are found in the southern most parts of Chile and Argentina. The summers are cool because these areas are located very far from the equator -at Punta Arenas in Chile located at 53 degrees South the temperature of the warmest month is only 52 F ( 11 C) and the coolest 35 F ( 3 C ). The range is therefore only 17 F. This calls for an explanation. Please note that as expected from a such a high latitude the summer temperature would have been around 68 F which is typical of cool-temperate climate( London has 65 F ). The reason is that the southern most tip of the continent of South America is very narrow and remains under the influence of both the Pacific and the Atlantic oceans. Consequently the summers are cool and winters mild. The rain is light and is uniform throughout the year. The total annual rainfall at Punta Arenas is 16 inches ( 400 mm ) but even such a low rainfall is sufficient to sustain vegetation since evaporation rate is retarded at such a low temperatures.
Central Chile exhibits the typical Mediterranean climate of dry warm summers and cool wet winters. The max temperature at Santiago, Chile located in the heart of this region in the hottest month of January is 67 F ( about 20 C ) and min in the month of July is 46 F ( 7 C ). The total annual rain fall is 14 inches ( 350 mm ) of which more than 11 inches or 80 percent falls in the winter months from May to August. January is practically dry. The temperatures in the hottest month are less than the other Mediterranean locations in the Northern Hemisphere ( Rome 76 F ) because Santiago is under the influence of cool pacific current in summer.
Almost all of the pacific coast of South America which contains a major part of Chile and south western Argentina depicts this type of climate. This is a very narrow strip which runs along the Andes mountains and on the other side is the pacific ocean. This is the reason that the stations located in this part of the world do not have that extremes of temperatures which are found in the Northern Hemisphere Deserts but the ares are one of the driest places on earth. Antofagasta at 24 S and 70 W lies in the heart of the Atacama Desert of South America which is known for its dryness all over the world. Although the warmest month is 72 F ( 22) and the coolest month is 61 F ( 16 C ) at Antofagasta which does not show any extremes of temperatures but the rainfall is practically NIL in each month leading to a total annual rainfall which is negligible. Indeed there are some areas in this region which have not received rainfall for the last 400 years.
A very long Mountain range runs across the western edge of the continent between about 10 degrees North Latitude and 50 degrees South Latitude and is among the longest mountain ranges of the world. This is called the Andes. It contains many important cities of South America like Quito in Ecuador, Bogotá in Columbia and La Paz in Bolivia. All these cities are located 2000 m ( about 7000 feet) above mean sea level. As we know that the temperature falls 1 degree F for every 300 feet or 1.6 C for every 1000 feet so the altitude modifies the temperature of a place to a great extent. The typical example of the effect of high altitude on temperature is that of Quito in Ecuador which lies directly on the Equator and being an Equitorial station one expects a constant hot and wet climate with unbearable humidity but due to its elevation of about 10,000 feet the climate is very pleasant. The temperature remains in the range of 54-55 F ( 12-13 C ) throughout the year and gives the effect of an English Spring. That is why areas like these are called lands of perpetual spring. The rain however is heavy and is equally distributed through out the year,
This concludes the account of climatic zones of South America which is not a thorough account but touches all the important features of different climates found in this continent