Weather: South America
Bone-dry deserts overlooking tropical oceans, perpetual windswept chill, hushed tropical splendour – South America isn't lacking in climatic variety. As opposed to the chameleon-like seasonal shifts found in Asia and North America, South America specializes in more-uniform climates that maintain their bold, distinctive hues throughout the year.
Despite the “South” in its name, a good fraction of South America lies in the Northern Hemisphere. The continent's gracefully tapered form is at its widest just south of the equator, accommodating the stunningly broad Amazon Valley along more than 2400km/1500 miles from headwaters to Atlantic. This is one of the world's lushest areas: the rainforest and its ecological diversity thrive in an environment where rainfall is generous and temperatures seldom get much below 20°C/68°F or much above 35°C/95°F. The northernmost reaches of South America are also quite moist, with the perplexing exception of the arid, scrubby Caribbean coast.
If the Amazon is the heart of South America, the continent's backbone is the improbably long chain of mountains that runs nearly the entire length of the Pacific coast. The volcano-studded Andes are actually a set of several parallel chains, with many peaks extending above 4000m/15,700ft from western Colombia to central Chile. Together, the Andes serve as a barrier that keeps cool Pacific air bottled up against the west slopes, while heat and humidity rule the tropical east. The long, gentle curves of the Andean spine combine with distinctive ocean currents to produce jaw-dropping weather contrasts from one stretch of shoreline to another. On the Colombian coast, it rains as much as anywhere else in the Western Hemisphere. Further south, where Peru meets the Pacific, it hardly rains at all. The only thing that can alter this regime dramatically is a famous pair of offspring from the Pacific. During El Nino, the waters off Peru can warm by more than 6°C/10°F, triggering rain across normally dry areas but encouraging drought across northern South America. The cooler-than-normal waters of La Nina have the opposite effect – they tend to reinforce the patterns that make one spot run dry and another wet, producing weather that's “normal, only more so”.
South America narrows as it extends into the southern mid-latitudes, so there isn't quite enough continent to produce the kind of bitter cold one finds across Canada or Russia. Instead, the oceanic westerlies maintain a cool, breezy grip. Storm systems in this persistent flow dump enormous amounts of rain and snow on the west slopes of the southern Andes. On the other side are the bright, thundery pampas of Argentina and, further south, the barren, chilly uplands of Patagonia.