When it is summer in the United States, it is winter in Peru. Still, Peru is close enough to the equator that it does not typically get as cold as it does in the south of the United States. This year, Peru is experiencing an unseasonably cold winter, though, and it may well be below freezing at night while we are in the mountains.
We recommend that you dress in layers. The difference between the daytime and nighttime temperature in the mountains can easily vary as much as thirty degrees.