Today when I went out, it was feeling like -34 c. I wore a boot, which had said that can cover till -30 c with a regular pair of sock. I was fine for first 30 minutes. Then my toes started frozen and I started feeling tremendous pain on my feet. I started walking to keep my blood circulation through toes and I felt little better. What I have learned from this situation is I have to wore thermal socks if the temperature became below -30 c.