Weather varies from region to region in Peru, so you’ll probably want to take a variety of clothes that’ll see you through no matter where you are.
If you’re delving into the Amazon Rainforest, it rains most of the time. It’s even wetter during November-March, which is also the time when it rains in the Andes Mountain region (where Machu Picchu is located).
The coastal regions are mostly dry throughout the year and are hottest during December-March, making it a great destination to get away from the Northern Hemisphere cold! This is also the warmest, sunniest time to visit Lima. In May-September, Lima is often shrouded in dense fog (“La Garua”) and can be drizzly. Of course, this is the driest time of the year to see Macchu Picchu, so if your Peru tour includes several parts of the country, you will probably have to come prepared for all weathers!