Seasons in the southern hemisphere mirror those north of the Equator, so South America cruises, particularly those that sail around Cape Horn, are limited to the summer months of November through March. In the northern-most embarkation ports, such as Rio de Janeiro, Buenos Aires, or Valparaiso, daytime temperatures can rise to the mid-80s F and higher, accompanied by muggy humidity, while nights cool down to the high-60s F. The further south your itinerary takes you, the cooler the temperatures. Expect daytime temperatures no higher than the mid-50s F in Punta Arenas, Chile. You may encounter near wintery conditions as you pass Cape Horn and cruise close to glaciers.