The best season is the dry period, and this is between May and October. During this time, there is little to no rain in the Andes. In the mountain rainforest, where Machu Picchu is located, it can rain all year round, but the rainfall is less between May and October.
But of course, there is NO here is no guarantee of dry conditions in rainforests.
The nights can get very cold in the dry season in South America. Depending on the altitude, the thermometer can fall below minus 5 degrees. Therefore, it is always important to have warm clothes with you.
Unlike the Inca Trail, which is completely closed in February, the Salkantay Trek to Machu Picchu can be done all year round. In the summer months between November and April, it rains more often, but the temperatures at night are much milder.
No matter what time of year you do the Salkantay Trek, you should always expect rain and have rain gear in your luggage.