The above average temperatures - expected to be between seven and 12 degrees C - are down to thick cloud cover spreading out from northern and north-western areas of the country on Tuesday and Wednesday.
The origin of the cloud - low pressure system "Bernd" centred near Iceland in the Atlantic - will also give rise to a growing area of rain in north-western Germany on Tuesday, which will spread across most of the country over the following two days.
The rain will bring with it strong winds all across the western half of the country, in places rising to gale and storm force, DWD reported.
And except for a brief lull, the mild temperatures, widespread cloud and high winds will continue through to next week, meaning the vast majority of Germans will not be seeing any snow this Christmas.
The only possible exception will be the south-east, especially southern Bavaria, where a high pressure system coming down off the Alps is expected to bring foggy conditions and consistently lower temperatures of around around 2 degrees C.