I love my tube scarf! On a recommendation here on BF, I got one of the Buff brand. It is lightweight merino wool, which means it is comfortable in a very wide range of temperatures. The pictures above show the various ways to use one.

I also have a merino wool cycling cap with ear flaps. This morning's ride had 34°F weather with high wind. I pulled down my ear flaps and wore the scarf like the third picture except that I also had it around my jaw. My jaw gets cold easily. With this setup, I was perfectly comfortable.