The weather in Peru varies from region to region. Please see below of a short description of what you can expect in the different tourist areas:
Lima tends to be rather humid and warm all year round. For travelers staying in Lima, they should pack loose, cotton clothing if travelling during January through to March. Between March and April, travelers may need something warmer to wear at night. During December and April is the best time to visit Lima, as the weather is mild and the sun is out. It hardly ever rains in Lima, so travelers wanting to visit need not worry about the weather.
This includes weather information about areas of Cusco as well as Sacred Valley and Machu Picchu. The rainy season is between November to March, thus the dry season is between April until October. However, do not be put off from coming to Cusco in the rainy season as it does not rain all day but usually for about an average of 3-4 hours per day and you will often get to see some sun. The average temperature fluctuates between 11°C and 13°C and during sunny days the temperature can reach up to 20°C. During the night in May, June and July, the temperatures can drop down to 7°C.
During the dry season between April to October, most of the days are sunny and warm, but the nights will get cold. During the rainy season, the days can be warm and have periods of rain but also periods of sunshine.
The weather in Arequipa is generally nice all year round. It is sunny during the day and is warm during the night. Even during the rainy of November to March, it hardly ever rains, thus is a good tourist destination all year round.
The Peruvian Amazon
All year round, the Peruvian Amazon has temperature betweens 15°C to 30°C, but rains heavily during the rainy season. During the rainy season, the Amazon features some heavy periods of rain but then may be dry for a few days before continuing the cycle. If you are going to the Peruvian Amazon during the rainy season, make sure you take waterproof clothes with you.
Nazca & Ica
In this area of Peru, there is nice weather all year around and hardly ever rains. Most of the days are warm and sunny and stay warm during the nights. During the winter, the nights can get a little chillier, so you may want to bring something warm.
In this region of Peru, it is warm all year round (between 18°C to 28°C) and hardly ever rains. During the summer, it can reach temperatures of between 25°C to 35°C. We advise you to dress lightly for this region of Peru and make sure you take sun screen with you.
Note that as much as we may like to, we can't control the weather, and even forecasting it can be troublesome especially in the Andes. However examining the weather trends and future forecasts can help, so head to the Weather Underground where you can look at current local weather, history and trends and even use their trip planner to see what the weather might be like when you're on holiday.