In general, when booking your flight to Lima, March is the cheapest month on average.
On average, from most locations, when planning your trip to Lima, try to book your flight in the region of 49 days in advance for the cheapest prices.
From most locations, the cheapest day to fly to Lima is Tuesday. Most users found that departing on a Saturday was most expensive.
On average you can find the best deals on plane tickets to Lima when looking for flights with afternoon departure times.