Originally Posted by
apricissimus
For me personally, I cover my ears below about 40ºF, and I cover my face below 10ºF. But it depends on what you're used to.
I've got a thin balaclava I use below about 45. It's one that can be used as a hat or balaclava, and I usually use it as the balaclava because it's more comfortable that way and I know I'd feel silly riding around with a cold face and face part under the helmet.