During our trip to Peru, the weather will vary quite a bit, depending on what part of the country. Here are some forecasts:

Lima Peru Weather - Friday, June 16 - 74°F (23°C) | 62°F (17°C) Partly Cloudy

Puerto Maldonado (Amazon Jungle)- Saturday, June 17 - 86°F (30°C) | 73° F (23° C) Chance of Rain

Puerto Maldonado - Sunday, June 18 - 87°F (31°C) | 71° F (22° C) Sunny

Cuzco (in the Andes) - Monday, June 19 - 59°F (15°C) | 35° F (2° C) Sunny

Cuzco (in the Andes) - Tuesday, June 20 - 60°F (16°C) Scattered Clouds

I can't find any forecasts after that. Basically, it will be warm but not hot in Lima, very hot in the Amazon Jungle, and then cool in the mountains, and it may dip below freezing in the evening in the mountains. Not the easy trip to pack for, weather-wise.