The Argentine Republic is a large country about one-third of the size of the United States. The centre and east are mostly low and flat, but the west is very mountainous rising to the Andes peaks, some of which reach over 22,000 feet. The northern Andes have surprisingly low precipitation so that the snowline may be as high as 20,000 feet. The southern Andes have much more precipitation, and there are many glaciers and permanent snowfields.
Because of these great altitude and latitude differences, there are many weather and climate differences. The country can be split into four broad climatic regions: the east central region (Pampas); the north-eastern interior; western Argentina and southern Argentina (Patagonia). The distinctive mountain climate of the High Andes should also be added.
East central Argentina (including Buenos Aires) also known as the Pampas, has an adequate rainfall of between 500 mm (20") to 1,000 mm (40") per year. The area has mild winters and warm summers within more rainfall during the summer months. Most of the rain falls on just a few days, so that wet changeable weather is not frequent, but the rain is often heavy. Average daily maximum temperature at Buenos Aires range from 14 °C (57 °F) in June and July to 29 °C (85 °F) in January. Average sunshine hours per day range from four in June to nine in the summer months. The region does not often experience heat or cold extremes, but frost may occur in most winter months but is not prolonged or severe. This is the most important agricultural region of the country and occasional drought is the main economic hazard.
The north-eastern interior has a warmer climate than the Pampas and, towards the north it is tropical or near-tropical. Temperatures remain quite high throughout the year, average daily maxima at Santiago varying from 21 °C (70 °F) in winter to 36 °C (97 °F) in January. An extreme temperature of 46 °C (115 °F) has been recorded in one January. The combination of heat and humidity may be uncomfortable in summer, as this is the cloudier wetter season. Occasional cold spells in winter may bring temperatures near or below freezing for a few hours, but generally the winters are mild or even warm. Average sunshine hours per day are similar to the Pampas region.
Western Argentina is a dry region. Even on the highest peaks snowfall is light. The eastern slopes and foothills of the Andes form a semi-arid region and the lowlands are virtually deserts. Annual rainfall of less than 250 mm (10") is not uncommon. Droughts are frequent here and often prolonged. Rainfall is more frequent in summer months which are often hot and sunny. Sunshine hours range from 10 hours per day in summer to about 7 in winter. At Mendoza daily average maximum temperatures range from 15 °C (59 °F) in winter to 32 °C (90 °F) in summer.
Southern Argentina is a dry region with (in terms of temperature and changeable weather) a cool temperate climate not unlike that of the British Isles. The dryness, however, is unusual for such a high latitude. Towards the west of the region, rainfall is greater as cloud spills over the western side of the Andes. In the extreme south of the region, the summers are distinctly cool. The winters are long with frequent frost and snow, but the ocean's influence ensures that the cold is never prolonged or severe. The summers are generally cool and cloudy with brief spells of fine pleasant weather.