Peru spans the Andes Mountains, Amazon rainforest, and the arid Pacific coast, and is a true year-round travel destination with rainfall and average temperatures varying significantly at any point of the year by region and altitude.
Since the vast majority of travelers visit Machu Picchu in the Andean highlands, the best time to visit Peru is during the dry, cooler season from May to November, with tourism peaks from June-August.
The wet season from December to April isn’t a bad time to visit if you want smaller crowds and some good discounts and promotions, but you will likely encounter frequent afternoon showers and some muddy trails. Of course, the rainfall is also accompanied by greener hillsides and colorful orchids and wildflowers in full bloom.
A good alternative that combines warmer temperatures, small crowds, lower prices and fewer showers are the shoulder seasons from April-June and September-November.
In a country as geographically diverse as Peru, local weather patterns vary greatly, and in fact, it's not uncommon to experience all four seasons in a single day.
When to visit the Andean highlands (Machu Picchu, Cusco, Sacred Valley and the Inca Trail)
April to November, during the dry season in the highlands, is the best time to visit these popular destinations. You can count on little or no rainfall, hours of uninterrupted sunshine, and great views of the jagged Andean peaks of Peru. The rainy season from December to March experiences much more precipitation and temperatures that get downright cold very quickly once the sun sets.
When to visit the Amazon jungle
While humidity in the rainforest is high all year, the dry season (May to September) is the best time to visit the Amazon, and temperatures can actually get as high as 32º C (high 80s/ low 90s F). The rainy season, from October to April, is characterized by consistent daily rains and cooler nights, making it a less desirable time to visit this part of the country, but it is a rainforest, after all.
When to visit the Pacific Coast & Lima
The desert coast is arid, yet cloudy and cool most of the year. From January to March the sky is clear and the air tends to be warm and humid. Ocean temperatures make it a great season for swimming in the cool waters of the Pacific. Peruvians go to the beach at this time. Note that even during the warmer season, the Antarctic Humboldt Current does bring chillier water right along the Peruvian coast all year round. The rest of the year the gray coastal mist known as “garua” moves in, the sun is rarely seen, and the waters can get pretty cold.