Fleece is one of the best fabrics in the cooler months of the year. It keeps baby dry, even when he sweats, and it's a nice and easy layer that isn't too bulky.
And reducing bulk is important because you never want to compromise car seat safety.
Amazon is having a great sale on fleece and sweaters for babies right now and you don't want to miss it. This unisex Columbia baby and infant bear bunting is marked down from $45 and depending on what color you choose, you'll spend between $29 and $32 on it.
Not too bad. Especially because it's unisex ... remember, if you're planning on having more kids, unisex clothing is the way to go.