When is the best time to go trekking in Peru? Is it year-round? What are the best and worst months?

Trail conditions are best during the dry season, from April/May through September/October. I’ve done plenty of trekking in November, December, March and April but avoid January and February because those are the rainiest months. I think April and May are the best because it doesn't rain much but the hills are still green and covered with flowers.

Note that the Inca Trail is closed for maintenance during the month of February.