Peak season in Machu Picchu and Cusco is from June to August when tours and accommodation are usually booked out well in advance. An ideal time to visit Cusco and the Sacred Valley is right before peak season in April – May or just after peak season in September or October before the rains begin. The weather is good during these periods and everywhere is less crowded. Cusco, Machu Picchu and the Sacred Valley have just two seasons – wet (summer) and dry (winter).

Rainy season:
The rainy season usually begins in October and runs until March with January and February being the wettest months. The rains can be fierce when they hit, causing landslides and disrupted transportation schedules. Major rains in 2010 led to landslides and the closure of Machu Picchu as well as difficulty accessing parts of the Sacred Valley due to bridges being washed away and roads damaged. Average temperatures during the dry season range from 5 degrees to 19 degrees.

Dry Season:
The dry season runs from April until September. June and July are the driest months but also the coldest with temperatures sometimes dropping below zero. Average temperatures during the dry season vary from o degrees to 25 degrees during the day. Temperatures tend to rise around noon due to the strong daytime insulation and the transparency and dryness of the atmosphere. Similarly, the loss of solar radiation can cause temperatures to drop below zero in the evening, night and early morning.