Due to the El Nino, all the coastal area is going to be very hot. However, from past experience, I can say that all cities in the altitude have a variable weather. That said, it will be very very hot if you're standing in direct sunlight. If you're in the shadows, the windchill will cool you down very fast. And at nights, it will be very cold.
Peru is not a country where you can say "we're just going to have a hot humid weather during this season". It is known for having all kinds of weather combinations all around the country, all around the year. Even in Lima itself, you can have several micro-weathers inside an area. I would say that's something to experience :P