People usually think merino wool for winter, but it also works great in summer.
1. Breathable: The wool fibre is special and has the ability to move moisture in the vapour form. When you sweat, you sweat in the vapour form. The merino wool absorbs the vapour, and then passes it to the outside. The merino wool fibre can also absorb up to 30% of it's weight in moisture vapour, leaving your skin feeling dryer, and more comfortable. This is why a lightweight wool t-shirt feels great on a hot summers day.