South America is a huge continent (it crosses both the Equator and the Tropic of Capricorn), and climatic conditions vary widely. In June, when it's freezing cold at the southern tip of Argentina, it's hot and humid in Venezuela. You can take into account, however, that more than 75% of the continent sits south of the Equator, which means that winter usually lasts from June through September and summer from December through March. In high-altitude cities, such as Quito, you can expect cool weather year-round; in the Amazon basin region -- in the center of the continent, from Ecuador to Brazil -- the weather is hot and humid year-round.
In general, the high season for travel in South America lasts from June through September, from mid-December through mid-January, and during Carnaval, which takes place the week before Ash Wednesday. The ski season in Chile and Argentina reaches its peak in July and August.
Holidays, Celebrations & Events -- Many of the holidays and festivals in South America correspond to Catholic and indigenous celebrations. (Sometimes they are a mixture of both.) The entire continent seems to turn into one big party zone during Carnaval, usually in February or March. During the solstices and equinoxes, many indigenous groups, which historically have worshipped the sun, organize traditional celebrations throughout South America.
