How to stay warm while hiking without getting soaked in sweat?

I recently finished hiking Acatenango and Fuego in Guatemala. It was an incredible experience, but also challenging—especially the 4 a.m. summit hike. I didn’t sleep the night before due to mild altitude sickness (rapid heartbeat and trouble catching my breath), which made it tougher. Still, I had a great time overall.

One of the biggest issues I faced, though, was staying warm while hiking. Due to the heavy pack, I sweated a lot, and within minutes, my back would be soaked, which eventually wet my fleece. For context, I wore:
• Base layer: Merino wool leggings and athletic shorts, plus either a Lululemon dry-fit T-shirt or a long-sleeve Smartwool hiking shirt.
• Mid-layer: A Marmot fleece which would come on and off
• Outer layer: I added a down jacket when it got cold, but I had to be careful to avoid trapping moisture in the puffer so I mostly just wore it during breaks.
• Pack: A 50L Kelty pack

Once I started sweating, it was hard to stay comfortable. My fleece would get wet, and when the temperature dropped, I had to balance layering up without letting sweat soak through to the down jacket. I came back feeling fine (no sickness), but it wasn’t the most comfortable experience. I’m going to Madeira and the Azores soon so hoping to find a solution before that.

For anyone who deals with similar issues:
**How do you prevent your mid-layer from getting soaked?
Are there tricks or gear recommendations to manage sweat better? ** I’m thinking maybe one of these bags with some sort of trampoline back like Osprey Exos.

I’d love to hear what outfits or systems work for you! Is hiking with a wet back just something I need to accept, or are there ways to improve this?

It’s about adjusting to being ‘comfortably cold.’ Start with minimal layers and only add more when absolutely necessary. For instance, wear a Smartwool quarter-zip and add a light fleece or weather jacket depending on conditions. Always carry dry extra layers to change into when you stop.

You might be wearing too much. I start cold and warm up with movement, using layers like a Patagonia capilene t-shirt and a mid-weight baselayer. For colder temperatures, I add a Patagonia R1 or R2 fleece. Consider the breathability of your fleece; some may retain more moisture.

A fleece vest might help by keeping your core warm while letting your arms ventilate excess heat. Adjust your layers before you start sweating too much, and have a system where you can quickly change or adjust layers during breaks or changes in activity.

Layer management is key. Have a good wicking layer and an adaptable insulation layer. Use a shell layer for wind or wet conditions and adjust layers before you start sweating. Consider carrying an extra base layer in your pack for changing into once you reach the summit or stop for longer breaks.

Adjust your layers before you start sweating. Use a thin base layer and appropriate outer layers based on the weather. You can also try using a lighter pack or a pack with better ventilation to reduce sweat.

I faced similar issues hiking Acatenango. I hiked in minimal layers, but once I stopped moving, I had to layer up heavily to stay warm. It’s a balance of managing sweat and adjusting layers quickly to avoid getting too cold when you stop.