Buy four pairs of merino wool liner socks at the same time. You need them anyway and get the 4-pack cheaper. These low, lightweight socks are excellent for hot weather. Made in Finland.
Need only one pair? We have those, too.
The heel has a fitted Y-construction to retain the heel and keep the sock in place.
Wool is an excellent material. It will keep you warm even when wet and does not soak in nasty smells or dirt easily, making it pretty hygienic. Now, Merino wool has two additional benefits compared to normal wool; it's finer, which means it's also warmer per gram and feels very comfortable against the skin, not rough and itchy at all.