Like all big mountain ranges, the peaks of the Andes generate and attract their own weather, making conditions impossible to predict. There are however two distinct seasons in the region, a wet season that occurs from November to March, and a dry season April through early October although as in other parts of the world this is changing and becoming a little bit less predictable. The dry season is characterized by cold nights with temperatures near freezing or slightly below in Cusco and Puno, but sunny days, with an average daytime temperature in Cusco of approximately 20°C to 22°C (68°F to 72°F). This can be considered a stable pattern, but be prepared for a wide range of temperatures, from freezing nights, to snowy and windy conditions, to bright sunshine intensified by high altitude. The wide fluctuation in temperatures makes it important to bring layers so that you are always prepared. The rainy season tends to have less diurnal temperature variation as the nights are warmer and the days not quite as hot due to the rains but when the sun does shine during this time of year the temperatures can be close to 25°C (77°F) but the sun’s intensity makes it feel much hotter.
The Amazon basin is almost always warm however there are sometimes cold temperatures that sweep down from the Andes, “friajes” which can catch people off guard. During a friaje the temperatures can reach as low as 15°C (59°F) which feels very cold with the humidity and lack of infrastructure for these climates. That being said, the day-time temperature is generally between 25°C to 30°C (77°F to 86°F) at the lodges but higher in the cities as you do not benefit from the same shade protection. Although it rains through the year in the Amazon basin, there is a marked rainy season during the same season as in the highlands during which there are many more mosquitos and you should be prepared for this.
The key to staying comfortable while on an active trip is layering. To obtain maximum comfort with minimum weight, you need versatile layers that mix and match to create the right amount of insulation, ventilation and weather protection. This gear list has been created to help you choose your clothing and gear for this trip. Try to bring only what is necessary.