Originally Posted by
Portis
Making one part of the body warmer has some effect on other parts of the body but the effects aren't linear, nor are they enough to compensate for a part that is inadequately protected.
It's true that you can warm up your fingers and toes by making sure your head (ears, neck) are warm. Certain body parts have priority, with fingers and toes getting short-changed if you're losing body heat somewhere.
But wool socks, looser fitting shoes, toe covers all help if you're wearing summer shoes.