Wearing a bulky or puffy jacket while in a car seat can reduce the effectiveness of the seat. So how to keep your child safe and warm? Use a Car Seat Poncho! This is an absolute must-have piece for kids during the fall autumn winter. The kids car seat poncho fits over the car seat straps and acts as a blanket while in the car, and no interfering with carseat harness, also as an extra layer of warmth outside.