I'll be backpacking South America for several months beginning in late May. I'm trying to figure out what clothes to bring. Temperatures will range from the 80s in the North down to the 30s in Peru or farther South. Strong wind and some rain will probably be present as well. I'll be hiking/camping sometimes (in the warm and cold), but also spending a great deal of time in hostels/around cities.

Items which can double as casual wear are a bonus as it's all going in one pack for 3+ months.

As of now I was thinking this:

- merino long sleeve base layer
- merino bottom base layer
- lightweight fleece (Patagonia R1 or Marmot Reactor)
*I've never worn fleece, and wearing 100 wt fleece in the store felt like it would offer very little warmth. Would a thicker fleece like a Patagonia R2 be too much?

- Hiking pant of some sort (street stylish would be nice)
- Light rain jacket or Wind Jacket (I own a North Face Verto Pro windjacket already, but was looking at real rain option such as the Marmot Mica jacket)

I also considered a puffy of some sort, but decided against it as I thought the above should suffice. Thoughts or suggestion of specific gear would be greatly appreciated!

Thanks!

Two suggestions. 35F with just a base and a light fleece would leave me just a little chill if I wasn't moving, I'd add one more layer, which for me, would be a fleece vest. At that temp a fleece headband or a Buff worn as one, would help, too. I like convertible backpacking pants, as the shorts option is good, they dry quickly and repel stains fairly well and the bottoms can be taken off if they get dusty/muddy and washed out separately. I also like the big pockets for maps, paperwork, and snacks. I wear mine casually, as they fit me very well. No one has booted me out of anywhere for improper attire...

For our hiking trips to Peru, we also added a puffy to what you are taking. Sometimes, that seemed to be the difference between sitting outside and admiring the view, and climbing into the tent and into a warm bag.

So we took a short-sleeved base layer that we almost never wore except to sleep, a lightweight hiking shirt, an alpaca hoodie sweater from Peru ($15 in the local markets), and our puffies.

Are you backpacking in terms of wilderness trekking with tent, food and sleeping bag (the focus of this site) or only in terms of budget travel (for which there are better, travel-focussed sites)?

In any case, do remember that May in Colorado is November in Chile (in other words, chilly--sorry, couldn't resist the bad pun! ) Also, if you are trekking up high, the altitude makes a big difference--as you should know from Colorado.

I'd take that puffy--or, as balzaccom suggests, shop the local markets for lovely warm stuff. Also the appropriate accessories for hands, head, feet--think Leadville (or higher) in November!

Had you thought of starting in Chile or Patagonia and working northward, so you aren't visiting there in the middle of winter? Although if you're leaving this month, you've probably already made your travel arrangements. In that case, think Leadville in January!

If in doubt, instead of getting everything here, you could wait and buy some clothing in South America, as needed. I was surprised at how much of the same gear we have here, you can get there. I would, however, invest in the best shoes you can get here and be sure they fit perfectly. I even have difficulty finding a pair or shoes that fit me here!

You probably will not be able to predict every possible weather condition, but each locality should have clothing and supplies appropriate to that location's weather. Bring clothing for normal conditions; buy locally any extra items for those odd-ball infrequent conditions.

Some places have mosquitoes or fleas/flies that carry diseases, such as the infamous sand fleas of Machu Pichu. These fleas that hang out in grass attack ankles. As silly as it seems, I took gaiters. I also took my "bugs-off" clothing- pants, shirt, hat and a head net.

This has nothing to do with "layering" but be aware that water quality is questionable at best, so be sure to have a good system for water treatment. Chlorine tablets are small and light weight and I would consider them an essential. Everyone drinks bottled water, but you could get stuck in a place where you have to drink untreated water. You should be able to buy locally the water treatment chemicals needed to wash produce. You need to treat tap water you use to wash produce. Almost ALL tap water is bad. My husband and I both got sick and his pro-biotic tablets were really helpful. I also had some electrolyte replacement powder (Emergen-C makes packets of these).

Tent, food and sleeping bag when I'm farther south many times, though I will be renting the tent and bag when I need it.

As for starting down South I was tempted, but I'm going to be taking Spanish lessons in Colombia to start and figured it would be better to learn some of the language first.

for what it's worth, the Spanish in the Andean countries of Peru, Bolivia, and Ecuador is pretty slow and easy to understand, and they are very cheap countries, good places to learn, in my opinion. I don't know about Columbia, but I suspect it will be faster and harder to understand. Chilean Spanish is way difficult. In any case, if you start north in May going south, the weather should be more on your side, except that Patagonia isn't really so great until more like November.
As for clothes, it isn't really any more cold or wet in Peru or Bolivia than in the US, despite the high altitude, based on my experience. Any clothes that work for you backpacking in the Rockies should be ok, I think, that's what worked for me. The only thing I wish is that I had had a nice light puffy (I bought my first one after getting back, partly because my buddy looked so much more comfortable in his than I was And Daisy's suggestion about hitting up the markets when you get there is not only cheap and practical, but also more fun. Better a souvenir alpaca wool hat than some boring american sold REI hat!
As for renting your gear there, well, that's a dilemma in my mind. I always brought my own for my various trips, I have always heard that it is hard to rent decent quality gear down there, something that you can rely on, so I never have. On the other hand, it is a drag to be hauling backpacking gear everywhere you go. And my trips were always only a month long, whereas it sounds like you will be traveling for quite awhile longer. But one gear note, I would NEVER suggest bringing a whisperlight international along, with the plan of using the easy-to-find kerosine: the kerosine is utterly nasty to burn. Ugh! You can use gasoline ok in the internat'l whisperlite, that worked for me the one time I did that. Otherwise, you can get fuel cannisters ok, but I would maybe try to bring my own Pocket Rocket from home, just so you don't have to find one...but that's just my perspective talking.
Most important of all, though, have a GREAT time!!! What a fun adventure! Let us know how it goes for you.

It won't help you much on the trail, but Chlorine bleach is still an effective water treatment method and should be available most everywhere. It would be a good idea to know how much bleach to add to water to purify it before you go. 12% industrial strength bleach has about 1 Lb of free Chlorine per gallon, 6% household bleach about 1/2 Lb of free chlorine per gallon. To know how much is needed, you need to know the Chlorine demand of the water to be treated. There are rules of thumb for almost everything, but I'm not current on this. It shouldn't be too hard to google this and come up with some reasonable treatment rate. One gallon of 6% bleach will generate a 1 PPM in 500,000 Lb of water or about 60,000 gallons. To get 1 PPM in one gallon would require about 1/16 of one Milliliter of 6% bleach. Normal Chlorine demand should be 5 - 6 PPM, so around 3/8 mL. At 20 drops per mL, around 7 - 8 Drops of 6% bleach per quart of untreated water. Normal minimum contact time is 20 minutes. A 1 Part per million concentration of Chlorine bleach has a bleachy odor. This is something that you can try at home to get some idea of what it is like in the field. If your water has had 20 - 30 minutes of contact time and it still smells bleachy, it's probably safe to drink. Excess bleach isn't good for you, but in the PPM range, it's less harmful than pathogenic bacteria. In small private water supplies, we have looked for a Free Chlorine residual of no less than 0.2 mg/L in the finished water product. This level would be well below the taste and odor thresholds for normal human beings. The military has probably developed guidelines for treating questionable water. They can't afford to have a bunch of troops out of action because of bad water. Most of the Chlorine Dioxide treatments require 4 hours of contact. This is primarily because the Chlorine Dioxide has to be generated before it can kill the pathogens. Bleach may not be as effective as Chlorine Dioxide, but it's active the moment that you mix it with the water to be treated. In a 1 to 10% solution, it's an effective surface disinfectant that can be used to avoid cross contamination. The 1 to 10% solutions are the actual dilution of household bleach, not the concentration of Sodium Hypochlorite in water. The washrags that your server wiped your restaurant table down with probably were a 1% bleach solution. Bleach is an effective disinfectant and is commonly available, a fact that should not be overlooked.

https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water

Edit: Add Link

keep in mind temperature reports, will you be staying in high altitude which can have vastly different weather than sea level in those countries.

I traveled costa rica for 3 weeks, and backpacked for 4 days in the jungle during that trip.

buy everything before your trip imo. very difficult to get things in costa rica as their roads/delivery infrastructure was crap. easier and cheaper to buy in the usa.

are you carrying your whole trip load while going through the outdoors? or will you leave your non outdoors stuff elsewhere. If you'e carrying everything I think youll need a big backpack, 85l minimum. I would buy everything then pre pack to make sure it figts.

there are certain you get cold in the outdoors. when you're not moving eg breaks, lunch, camp evenings and when you're sleeping. you need the to know what kinds of temp lows you'll face at night. You need enough insulation to sleep comfortable. I'm a cold sleeper, so in 32f nights are cold for me. I need a 32f comfort rated bag (or 15 degree "normal" rated one) + thin sweater + thick fleece sweater + fleece balaclava + pants + socks. I'd buy most of that gear on amazon.