Not only do my kids have light hair and blue eyes like D, but evidently they also inherited his body temperature. If I would let Jack wear a short-sleeve shirt everyday, he would. High of 40? No problem. He's got a jacket.
Anna also doesn't seem to have a problem with being cold. She sleeps in as little clothing as possible. And when she was volunteering at the community light display in very cold weather, she started out with a light shirt, sweatshirt and coat. She quickly dispensed of the coat and never felt the need to put it back on. Yes, there were a couple of portable heaters available, but unless you were standing directly in front of one, the heat wasn't overwhelming.
So on those days when the kids must walk home from school because I'm at the office, I will not feel guilty because chances are, the cold won't bother them at all -- unless it gets them sympathy and hot chocolate from grandma.