Peak season for visiting the Andean areas is between May and October. Outside of this period it can be rainy, although this offers the advantage of fewer visitors, greener scenery and abundant flora, including orchids at Machu Picchu. Invariably the Amazon is hot and humid year round.
Best time to visit the highland areas around Mach Picchu is April to October.   The summer rainy season from November to March can cause transport problems in the highlands, while the eastern lowlands are warm and steamy year-round.