Yes, we do still live in Michigan. No, I'm not crazy. I'm not comfortable with Tillie wearing a winter coat while she's in her carseat. I don't think it look comfortable and there's that teency small chance of the down compressing and ejection from the seat. I know.
Instead, I keep her Aden + Anais dream blanket in the car since it's pretty thick.. After I buckle her in, she lifts her hand up waiting for me to put the blanket on her lap, then I set her "blankie" on top of that. I think she's pretty warm in the car.
When we go into a store blankie comes with us and she has to wear a hat in and out of the store. She knows this and sometimes reminds me if I forget. Sometimes she resists, but I make her do it.
Oh, and I do keep one of her winter coats in the car, along with an extra blanket and gloves.