That's 5'C right?

I wear knee warmers if there's no left-over frost and no wind, if there is wind I wear "normal" non-bike leggings made from thick tee-shiort material.

If its rainy or frosty I wear some fleece lined long legged bibs we picked up on Pro-bike Kit.

Of course, I don't have to ride in snowy conditions, but I find as long as my knees are warm, my legs are ok. (And I have plastic bags inside my shoes to save my toes )