I understand your frustration as I feel most parents underdress their kids too. But, I am on them like crazy and telling them exaclty what I need and that thier child was cold etc. I do go inside if someone is cold enough to be crying as it isn't the child's fault that the parent hasn't dressed him/her properly. I then make sure to tell the parent that we had to go in because their child wasn't dressed well and was crying from cold. Make a list of what you require (be specific) and tell parents they need to supply it. Outside time is important to me too, so I really make sure they all have suitable clothing. I think sometimes parents don't spend any time outside themselves and so they don't realize how cold it can feel to be out there for an hour or more at a time. You have to tell them!