Keeping baby warm in winter

So my son will be born in late August, maybe even early September if not before his due date (8/27)

How can I keep him warm during the winter months without overdoing it? I’d hate to put him in a fleece bodysuit or something warm only for it to potentially be too hot for him at some point, and I’d hate to not put enough layers on him, making him too cold.

I was wondering if when he’s in a car seat if I could just have him in regular clothing and place a warm, plush blanket over him if that would be enough? I know better than to buckle him in with a jacket on. Does the same go for winter body suits? I could be overthinking this..but I appreciate any help you can give me. Thanks!