The first advice many smart babywearing educators will give is to dress yourself and your child in layers. Layers keep in the warmth and allow us to control the temperature by removing layers when we get too hot (it is possible to overheat so watch for that!). A woven wrap is a fantastic layer to add to your bundling repertoire, but where does it fall in the hierarchy of layers - toward the inside or the outside? The answer is found by considering several factors.
1. How likely are you to let baby down? A baby who is walking and curious about the snow and able to get down is going to need direct access to the outside of your layer sandwich, where a baby who does not have the option to get down could be lightly bundled and wrapped first, then be bundled fully.
2. How cold is it? Up where I am in the Pacific Northwest it usually stays above freezing so typically wrap over my layers because I don't need that extra protection. Sometimes it is particularly windy, though, so I will layer up, wrap, and then throw on a big sweatshirt or my husband's jacket as an added layer of cold protection. If you live in an area where it is consistently below freezing in the winter, it could be wise to invest in a babywearing coat or large coat to throw over you.
4. What materials are you wearing? If your jacket, or your baby's jacket, is slick, wrapping over it might be a more slidey experience. The opposite would be true is you're wrapping against fleece. Also if you have a particularly puffy jacket or a cushy load of layers, you may need more length to wrap over all that extra padding.
5. If you wrap over all your layers, make sure baby is covered. Especially if the air temperature is below freezing, all of baby's exposed skin except for the face should be covered. Use leg warmers to cover any gaps between baby's pants and their socks. Keep booties or an extra layer of socks over those little toes. Hats are a must for warm ears, especially ones that tie under the chin so they can't take them off while in a back carry! And a scarf can go a long way - wear one on your neck and it fills in the gap between you and baby to help keep their face and neck warm. Just make sure that airway is clear!
No matter how you choose to winter wrap, be sure you always have baby's exposed skin covered in below freezing conditions while always keeping baby's airway open regardless of air temperature. Dress in layers with baby in one more layer than you and watch for overheating cues: overly fussy, red skin, covered skin is hot to the touch (especially back of arms or neck). Happy wrapping!