Never understood that bs about girls being forced to wear skirts in winter. Where I live it gets to -40 to -45C before windchill a fair bit. That takes something like minutes for frost bite to set in. Though I don't know if Japan even gets half as cold. In order to cement yourself against the cold, its better to lower the temp of your house to like 15C if you can, the lower the better, but stay above 10C