If I'm going somewhere quick, where he will only be outside of the car or a building for a few seconds, I just zip him up in my coat. I turn the heat on in my car full blast so hes comfortable in the car, then when its time to go in somewhere, I put him on my chest, then zip up a hoodie over him (except his head), then zip up my coat (which is huge and fluffy so he has plenty of breathing room). I've done this a few times, and hes always fine after it. My car also has auto start, so I let the car warm up before we run back out to it. Hope this helps... I find it easier to do that, and quicker than to hassle with a carrier. I also think it keeps him warmer, bc my coat protects him from the wind/cold air, and my body heat helps keep him warm.