You can always add more layers or take off some layers of clothing depending upon how cold or warm you feel.
One more thing to keep in mind is the art of layering when it comes to clothing. It’s preferred to have multiple thin layers of clothing rather than a single burly — 50 degree down jacket! You can always add more layers or take off some layers of clothing depending upon how cold or warm you feel. The layers trap air between them, which acts as additional insulation and helps keep you warm. On most days, one thermal, a polyester t-shirt and a fleece are more than enough during trekking.