Temperatures can fall at times in the tropical forests of South America. The occasional phenomenon known in Peru as “friaje” (“cold spell”) can occur at certain times of the year, affecting both the southern highlands and the southeastern Amazon forests of Peru, as well as neighboring countries, and lasting for a few days at a time.
This effect is caused by the arrival of cold air masses from Antarctica. Normally, these do not penetrate as far as Peru, but when they do temperatures can fall in southeastern Peru, including jungle regions accessed from Cusco, such as Tambopata National Reserve and Manu National Park. These low temperatures can be experienced for periods lasting a few days, usually between April and August (although they may occur at any time of year), as polar air masses race up from the South Atlantic, passing through the basin of the River Plate in Argentina.
When it arrives, the “friaje” phenomenon tends to last for a minimum of three days. Some scientists believe that these cold air masses are able to penetrate so far north as a result of human action: deforestation means that much of the vegetative cover that once acted as a barrier to such incursions has been removed.
During the brief period that the “friaje” phenomenon usually lasts, particularly cold temperatures mostly affect those people living in the highlands, as well as their livestock, while in tropical forests a sudden drop in temperature also felt by locals and visitors alike.
The most dramatic “friajes” occur when such cold air masses meet warm air masses moving down from the equator, and settle for few days over southern Peru, northern Bolivia, and southwestern Brazil. When this happens, not only is there a drop in temperature, but also a rise in precipitation. The subsequent increase in humidity in forest areas makes the cool weather seem more penetrating, as jungle temperatures fall to below 15 degrees Centigrade (59 Fahrenheit).
An upside of the “friaje” phenomenon occurs after they pass. When the weather clears, sightings of wildlife increase due to feeding pattern changes: reptiles, including caimans and anacondas, emerge from the water to sun themselves, often creating an impressive spectacle.
Regardless of this occasional atmospheric phenomenon, at Tambopata Ecolodge we always recommend that our guests arrive with some warm clothing. We offer this seemingly counterintuitive suggestion because at any time of the year in the forests of the Amazon basin temperatures can be low during the early morning, particularly when traveling by river. Many of the itineraries offered by the Ecolodge involve early starts, as do the transfers from the lodge to the airport at the end of each visit, and so guests should always remember to pack something warm when visiting the jungle!!