South America is a destination to visit any time of year!

75% of the continent sits south of the equator (southern hemisphere). Hence, in the southern hemisphere winter usually lasts from June through September, and summer from December through March.

Here are some pointers of the ‘prevailing’ seasons the further south you travel from the equator (or south of Ecuador!).

June, July, August - the Winter months
September, October, November – the Spring months
December, January, February – the Summer months
March, April, May – the Autumn (Fall) months

Most regions are accessible all year round. But keep in mind the following:

Peru. Winter is dry season in Peru – the best time for trekking the Inca trail is April to October. The full length Inca Trail generally closes throughout February each year at the height of the Peru wet season. Machu Picchu should be accessible all year round.
Chile & Argentina (south). Winter is peak Ski Season in Chile & Argentina – the best time for skiing is June to August. Months of November to February are the best time to explore Patagonia with longer days to trek. Some areas of Patagonia may not be accessible during winter.
Argentina (north), Uruguay & Brasil. December to February is the peak season for beach weather in northern Argentina, Uruguay and Brasil. Brasil’s Carnival is at the end of February each year.

2007 South America Travel Advice