What clothes to take to Peru?

Travel Info
I am going to Peru for 2 1/2 months from Oct to Dec. I have a low luggage allowance on the plane (20kg!!!!) so I need to only be taking the essentials. What kind of clothes to I want to take?
I am going for a medical elective so I have to make sure that I have clothes suitable for smart work. I also plan on going travelling for about two weeks in December, what kind of clothes would be best for this.

Is it going to be hot/humid/rainy ect?
I've been looking at the weather in Cajamarca at the mo, but I guess it wont tell me much about what it's actually like to be there.

Thanks

Travel Tips

Lima will be hot, muggy and dusty, so take lightweight cotton,
casual. The mountains, like Cuzco will be cooler, sometimes
rainy so have some heavier clothing and rainwear. Since you
will be going to different areas, pack things that can be layered,
and try to stay in a range of colors that will mix and match.
We have travelled to Peru a lot, my husband is from there
and the mountains are the best. You can aways buy some
nice alpaca sweaters when you go to Cuzco, that way you
don't have to pack them for the trip.

Others
i can answer this since i was born there lol what city (ies) are you going to?