These are excellent for cold weather. Castelli designed them for temperatures in the 37º to 59º range but for some riders they would be good even below freezing while offering protection against damp conditions as well. This one comes with a 16cm cuff to protect the lower leg from wheel spray and is open on the bottom to fit over an MTB shoe, although it also works with road shoes.
The Castelli Diluvio shoe covers are made with 3mm Neoprene fabric will stand up to the wettest and coldest winter riding conditions. All seams are thermo sealed for complete water protection, with cleat and heel areas open for stability while walking. The stretchy material easily pulls over your shoes while O-ring construction at the top prevents water from running down your leg into the shoecover.