Merino wool outer socks work in any weather.
For what it is worth, I always wear two socks when hiking. I wear Keen Targhee II, mid-height, Gore Tex lined boots.
As regards socks, my inner layer is usually a thin microfiber to wick moisture and reduce friction. I favor navy blue or black, as the liners always get grimy from walking on floors, after you remove your boots for the day, and hand washing does not get all the staining out. I also use the next day's clean pair to sleep in the night before if my feet are chilly.
The outer sock layer is ALWAYS the thickest merino wool socks that my boot sizing will accommodate. I am an avid Smart Wool (brand) fan.
The issue is not warmth, your feet are going to sweat in most any weather you would walk a Camino in. The issue is cushioning. In my view, more is always better. The merino wool provides excellent cushioning, washes easily, dries reasonably fast, and wears a long time. it is is also widely available, worldwide.
I hope this helps.