For god's sake stop this
This story out of Mineola highlights that people STILL do this. Think about how hot cars are when you get into them on a hot or even a warm day. As the Nassau County police investigator says, "cracking a window on a 90-degree day doesn't do much."
This guy says it was an accident. In this case in 2009, it was deemed an accident, but still inexcusable.
Here's a video I saw from Weatherbug Meteorologist Jacob Wycoff on the Washington Post earlier this summer. It is compelling and illustrates how dangerous it can be, even, as he points out, on a day that is not particularly hot.