HELP!一段英文的结构分析,

HELP!一段英文的结构分析,
One Christmas was so much like another,in those years,around the sea-town corner now and out of all sound except the distant speaking of the voices I sometimes hear a moment before sleep,that I can never remember whether it snowed for six days and six nights when I was twelve or whether it snowed for twelve days and twelve nights when I was six; or whether the ice broke and the skating grocer vanished like a snowman through a white trap-door on that same Christmas Day that the mince-pies finished Uncle Arnold and we tobogganed down the seaward hill,all the afternoon,on the best tea-tray,and Mrs.Griffiths complained,and we threw a snowball at her niece,and my hands burned so,with the heat and the cold,when I held them in front of the fire,that I cried for twenty minutes and then had some jelly.
最后分句中的逗号后面that让我很困惑,它用在这里有什么与语法功能呢?最后我猜想是不是和前面的My hand burned so组成的so that结构,
我觉的不像是定语从句，因为非限定定语从句的话不会把that单独隔开前面加逗号啊，再说意思上也理解不通啊