Are the winter boots warm?

With 3M thinsulate and furry lining, the winter boots are very warm.

Are these snow boots waterproof?

Yes, the snow boots have waterproof TPR shell and water resistant upper. You can walk through the snow and have fun.

How do you keep them clean? Does the mesh get dirty easily?

Hand scrubbed with a little detergent or try washing machine. The winter boots have gusseted tongue, so the mesh won't get dirty easily.