Peru's climate varies depending on where you visit.
On the coast it is usually quite hot although during the winter (April-August) it can get chilly early in the morning and at night.
In the Andes there are two main seasons - wet and dry. The wet season runs from November to April and is wet but usually warmer overall. The dry season runs from May to October and has hot clear days but cold nights.
The only one thing you can say about the weather in Peru is that it is difficult to accurately predict. You can beautifully clear hot days in the middle of the wet season and hail storms in the dry season - it's one of the beauties of Peru.