Peru is home to such a range of climates, if you explore the entire country, you’ll need an entire range of clothing! Sticking to the Andes, around Cusco it gets a sprinkling of rain and gets very cool at night because of the altitude. The coolest months of June to August can actually dip down to freezing at night! Some hotels are known to give their guests hot water bottles at night, to keep their beds warm. While cool, it is also dry at this time of year in the Andes. The rainiest months in Cusco and the surrounding Sacred Valley are November to March.
In Lima, the rainy months are June, July and August, the opposite of Cusco. These are also the coolest months, where the highs may not reach above 77F / 25C. The cool temperatures continue into October, before they begin to warm up for the November – May range, which is also considerably drier.