Calais is in the subdivision of Pas-de-Calais of which it is a sous-prefecture. Though Calais is the largest city in the Pas-de-Calais department, the prefecture/capital is located in the town of Arras. Pas-de-Calais lies in the Nord-Pas-de-Calais region of France which is comparatively small to other regions as it covers only 2.3% area of metropolitan France. But it is an important junction between France and England.
The Nord-Pas-de-Calais region is divided into two geographical divisions; ‘Haut Pays' which extends from Ardennes mountains to the Boulonnais passing through Crete de l'Artois. The other division is the ‘Bas Pays’ which is the start of the big northern plain.
The south of Nord-Pas-de-Calais is mainly chalky which the northern region is covered with sand and clay. But the common factor is that the whole area is coated with silt.
The climate in Nord-Pas-de-Calais is rainy for most parts of the year, due to its proximity to the ocean from the north and south. The average temperature ranges to about 10°C(50°F).
The arrangement of watercourses is of standard size and its direction is opposite to that of the Paris Basin. 69% of the region is cultivated for agriculture, while only 8% is covered by forests. Nord-Pas-de-Calais is the least forested region in France.