The boot says that is good to like -40.  I don't think so unless you keep moving.  Standing around my feet got cold even in temps near freezing.  If I was moving around things were fine.

I think the real issue is the boots do not come in half sizes.  So I am a size 11.5 and had to buy a 12.  The extra space in the toe is not conductive to keeping my feet warm.  I may need to wear two pair of socks to solve that problem.

The boots are easy on and easy off.  Use them around the barn and when taking care of snow.  They seem to be totally water proof as well.