Why are winters especially cold in northeastern France?

Winters in northeastern France are particularly cold because the region is primarily influenced by a continental climate, which contrasts with the milder oceanic influences found in the west.12

During the winter months, eastern France frequently comes under the influence of a continental high-pressure system. This system brings extremely cold conditions and often leads to temperature inversions, where cold air becomes trapped beneath warmer air, resulting in fog and urban pollution. Consequently, the plains of the northeast experience significant frost—averaging 83 days in cities like Strasbourg—and can remain under snow cover for several weeks at a time.12