In reply to THE.WALRUS:
We were there in our autumn- September/October (I think- it was 12 years ago!). Weather in Arequipa region was dry, no rain at all when we were there. I think there is a wet season (well, wetter- it’s desert overall) but not sure what time of year it is.
Huayhuash are was different- rain/snow every day, always in the afternoons
What are you planning to climb?