In the first three parts there is Christmas week, with about 2 feet with snow on the ground. Then , the next week of investigation, all the snow is gone, and the frozen lake is clear open. Although the plot happens during late
Ddecember, early January, the scenery changes from full winter to spring. Spring happens from mid-April in Sweden.
On the gravestone of Richard's family grave, the family name is spelled "Forester", while in the end credits it's always spelled "Forrester".