parents out there … clue me in, but isn’t this the pinnacle of irresponsibility, even on a cool day?

What she did is reprehensible, irresponsible, disgusting. That said, letting your baby finish their nap in a climate controlled car used to be very common. You could park down your driveway, leave the car on, bring in your groceries (and even put them away), and then get the baby out, but now able to give him your full attention. It’s not acceptable to do that today. I have spent so many many hours in my driveway letting my baby finish their nap. Apparently if you remove the car seat from the base the angle is more dangerous for them to rest at, but unbuckling her means the end of a nap. I have wished it was safe to leave her in there alone every time and if I was a slightly less informed mother, I probably would. I would say if the car is climate controlled it’s probably the same amount or less dangerous than co sleeping and like half of parents do that (I do not). Parents make a lot of choices.