We go out all the time, in all weather. I stress this in interviews and in my contract and policies. It is the parents responsibility to ensure that their child is dressed appropriately.
If a child arrives without proper gear, I will call them and it needs to be dropped off or child needs to be picked up. Yes, I've done this. Multiple times to one set of parents. No one has termed or complained (to my face, lol). They signed on knowing that the outdoors is a BIG part of my program.
If going outside is important to you, make sure your parents understand that and are willing to put the effort into clothing their kids properly.