You can only get ill from germs not the cold. If you put hot water in the tray before the children arrive it usually stays warm for an hour or so outside (depending on how cold it is though). The children love to see the steam rising from the tray, an opportunity to see water evaporation they would miss if you didn't. It's difficult sometimes for others to change the way they work especially if they think they are doing their best for the children. You may have to get them on board first before making changes.