Patagonia packing help

Solution? Having lived in a rain forest…my advice is to use layers of merino wool clothing and a water resistant shell.

I'm in Santiago (has been hot here) ready to meet my Patagonia tour now. It's going to be a different season for you, but I really worked hard on my packing list. Are you a carry on only devotee?
I really wanted to use my Peak Design 35 liter backpack but although it zipped, barely, I could tell getting things in and out was going to be a huge pain over 3 weeks so swapped for my international carry on size July wheeled suitcase.
At the boarding area leaving the US to Santiago, some folks were wearing their full-on hiking regalia. So much gear! Same with the airport, on arrival. So depending how "hike" is defined, you could go that route.
I know a wind/waterproof jacket is an absolute must, and same for the over pants and waterproof mitten/glove covers. And waterproof ankle protection boots if it's really hiking vs walking.
Since the lows are sometimes dipping to close to the 30s F I took an anorak shell to wear over a very lightweight puffer, instead of my heavier duty rain jacket with the summer weather now.
I've got a few merino socks, one merino long underwear set, a lightweight merino hooded sweater and a lightweight cashmere neck gaiter I pull up as a hat. Two sets gloves, one like a liner, the other medium weight. Two medium weight hiking leggings- maybe for you take a heavier pair, for the cooler temps.
That's my Patagonia side of the clamshell suitcase contents!
I started looking at the 10 day weather predictions a few weeks prior to departure.
Hope this is a start!

Thanks so much, Bon Voyage! That was quite helpful. I will pack a regular suitcase rather than a carry on. I don’t want to wear my winter coat and heavy pants on the plane and want some extra space. My biggest fear is the airline losing my case.

I'm not sure what the weather will be like in March/ April, but I'm in Patagonia now and the weather has been all over the place. We've had 70s and sunny (like today) but also a few days that we couldn't do much because the winds were dangerously strong. Lots of layers and definitely waterproof gear. The weather here has been similar to Iceland.

Layers are key.

It will be hot in Iguazu and much cooler in TDP and Perito Merino.

Definitely take a packable waterproof wind jacket and a fleece. Hiking pants that dry quickly and wind/rain pants.

A beanie or other hat that won’t blow away, gloves or mitts and good socks.

I went in October.

I did a very similar trip in March of 2024. I visited Iguazu Falls, Buenos Aires, a few different parts of Patagonia and also Mendoza. I had all kinds of weather, from hot and humid in Puerto Iguazu, to hot and dry in Mendoza, to hiking in an actual blizzard in Patagonia. And I managed to pack in only a carry on suitcase and a small backpack. It's one of my packing feats that I'm more proud of. While others on my tour were constantly paying for overweight luggage, I never paid a penny for anything I took with me on any of the 10 flights I took on that trip to Argentina.

For Iguazu the best decision I made was packing a comfy pair of board shorts to wear to the falls. I wore them two days in a row, visiting both sides of the falls and it was great because they were fine getting wet in the spray from the falls and then dried quickly once I wasn't in the water anymore. I paired that with workout tops that dried quickly and it worked out amazing.

For Patagonia, definitely bring layers. I had pretty chilly weather when I was there, so I did a wool t-shirt (short or long sleeve depending on activities) then a fleece zip up, a puffy vest and a waterproof jacket on top, plus a beanie and gloves. At times I needed to wear all those things and at times I could remove a layer or two, but it was nice to have everything just in case. For bottoms I did a pair of fleece lined leggings for the hikes with waterproof pants that I could wear over the top in wet/snowy conditions. I also took waterproof shoes and wool socks.

I had a few other items in my bag, like a dress for dinners out in Buenos Aires and Mendoza and some light jogger pants for flights. Definitely bring some good bug repellent and I highly recommend a waterproof day pack. I packed one and it was useful to keep my stuff dry from the waterfall spray at Iguazu falls and also from the rain and snow in Patagonia.

You're going to have a great time. Argentina is such a beautiful and diverse country. It's amazing!

The weather here has been similar to Iceland.

I will keep this in mind for my trip, I know what you mean.

I'm glad you received helpful advice and as I begin my travel back to the US I will "second" what a gorgeous country this is- and Buenos Aires is beautiful!
There it was perfect summer weather, but I believe temps into the 90sF are not uncommon. What a contrast to the parks! I was as fortunate with weather as can be, with only one morning with some rain and wind. I wore my lightweight water/wind proof anorak with its hood over my lightweight puffer (SO many Patagonia puffers around!), a merino wool sweater and a Paka blend long sleeve top. I wore my light cashmere "snood" just about all the time. Midweight pocketed hiking leggings but a thermal lined pair would have been wrlcone. And my waterproof hiking boots (Vbae barefoot with thermal insoles) for days with hikes vs walking. And gloves.
It's that wind! One beautiful day in Torres del Paine it was so very windy the rangers closed a planned short hike up to a lookout. I am a small person and, as in Iceland and the Scottish Hebrides, I was blown sideways several times.
I was just barely warm enough. I didn't bother with my rain pants the one rainy day, but would have needed them if we were out much longer. A benefit I find to cold weather travel is the ease of rewearing the layers under your outwear - I hang them inside out and spritz with a pretty fabric spray.
I was able to zip my light puffer into itself and fit it in my personal item backpack.
For the most part underwear and my two tees dried overnight.
Safe travels!