If you haven't seen it already, this article explains why you shouldn't allow your little people to wear snowsuits - or other similarly bulky/padded clothes - in their car seat. The basic idea is that the bulk of these doesn't allow you to tighten the straps of the car seat as tight as you normally would. As these snowsuits are really all air, in a collision, the air is squeezed out and suddenly, your little is rattling around in their car seat, not properly strapped in.
It makes a lot of sense, and since I saw it, I haven't dared put Isabelle in anything bulky like that in her car. That said, it's winter. It's cold. She needs to be warm and, sometimes, normal clothes, a coat and a blanket just don't quite cut it.
I accidentally came up with a great solution to this problem after getting a bit excited in the Next Christmas sale. Although I thought I had ordered a snow suit, when it arrived it was actually just a onesie with a fur hood. It's fleecy and warm, but it's thin and not anywhere near as bulky as a normal snowsuit. It's also MASSIVE on Isabelle. My little mind kicked in to gear, and I thought to myself..."I can use this as a snowsuit substitute over her clothes!" I felt like Newton when he 'discovered' gravity! Einstein and his E=mc2 business have nothing on me!
To me, it is the perfect solution. It's an all in one, and nice and cosy so it keeps Izzy really warm. As it's really big, it fits wonderfully over whatever she is wearing. But, it's thin, so there is no worry of it acting in the same way as a snowsuit if I were to be in an accident.
So, instead of taking a chance and using a snowsuit, or piling blankets on your little, simply buy a onesie in the next size up. I've already converted the mummies at my baby sensory class to my way of thinking, and hopefully you'll think it's a helpful little tip too.