A temperate climate
The Paris region enjoys a temperate climate thanks to oceanic influences. The average annual temperature is 11°C. Summers are mild (19.5°C on average), and winters equally so (5°C on average). A word of clarification: this average includes daytime and night-time temperatures. Summer daytime temperatures regularly exceed 30°C, and in recent years, as a result of climate change, Paris and the surrounding region have not been immune to heatwaves, with temperatures exceeding 40°C for several consecutive days. The temperature differential between inner Paris and the rest of the region varies between 1°C and 4°C. Average sunshine is around 1,700 hours per year, and cumulative rainfall is around 700 mm per year. Winds can be strong, but storms are extremely rare.
The Seine and its main rivers
The Seine. The Seine has an altitude of 59 m when it enters the commune of Villiers-sur-Seine, in Seine-et-Marne, and only 11 m at Port-Villez, as it flows out of the Yvelines towards Normandy: this gentle gradient is the source of a winding course where the river has gradually eaten away at the limestone cliffs. In its loops, the meanders offer a landscape of great beauty, especially downstream of Paris. In varying proportions, the Seine waters or borders many of the departments in the Paris region: in this sense, it remains a unifying geographical element at regional level.
The Marne. It flows out of the Picardy department of Aisne, crossing Seine-Saint-Denis for a short distance at Noisy-le-Grand and Neuilly-sur-Marne. Its course is dotted with guinguettes in the aptly-named Val-de-Marne, before joining the Seine on the right bank. The Marne receives water from the Petit Morin, Grand Morin and Ourcq rivers.
The Oise. It flows into the Île-de-France region from Picardy, not far from Royaumont Abbey. Its course divides the Val-d'Oise département down the middle: from Beaumont, it flows through L'Isle-Adam, Auvers, Pontoise and Cergy, before merging on the right bank with the Seine at Conflans-Sainte-Honorine (Yvelines).
Le Loing. This is a river in the south of the Seine-et-Marne département, running in a south-north direction. After leaving the Loiret, the Loing flows through Souppes, Nemours and Montigny, borders the Fontainebleau forest and finally flows through Moret to reach the Seine on the left bank.
The Essonne. A tributary of Beauceron origin, its course is identical to that of the Loing. After Malesherbes, the Essonne enters the department of the same name, flowing through Boutigny, La Ferté-Alais, Mennecy and Corbeil-Essonnes (a town which, curiously, takes the plural form). The Essonne is joined by the Juine, which on its left bank drains the towns of Méréville, Étampes, Étréchy and Bouray.
The Ourcq, Saint-Martin and Saint-Denis canals
Intimately linked by their network and history, these three canals have met the capital's water needs, as well as those of river traffic. Eager to achieve "something great for Paris", Count Jean-Antoine Chaptal decided to build the Ourcq Canal in 1802. Opened some twenty years later, the canal was subsequently extended by the Saint-Martin and Saint-Denis canals, which converged at the Bassin de la Villette in Paris. By 1825, almost 70,000m3 of water were being distributed daily in the capital.
The Canal Saint-Martin, which runs entirely through Paris, was only dug in 1822 and completed in 1825. Its lock bridges, which can be seen in the films Hôtel du Nord (Arletty's famous replica) and Le Fabuleux Destin d'Amélie Poulain, date from the second half of the 19th century. Today, the canal is a recreational area, with, at the Bassin de la Villette, the possibility of swimming in summer since summer 2017.
The 6.6 km-longSaint-Denis canal links the vast canal traffic circle (Parc de la Villette) to the Seine in Seine-Saint-Denis, avoiding the heart of Paris and the Boulogne meander, thus saving several kilometers.
The Canal de l'Ourcq, which has no locks in its navigable section (the watershed between the Seine and Marne rivers is crossed by the Villepinte trench), has become a water supply canal for industrial use, a communication route for pleasure boating and a place to relax on its landscaped banks. In Paris, but also in Pantin over the past few years, summertime events have become increasingly popular, and local residents are reclaiming these banks. The canals are home to several large and popular marinas.
Geology
Even if the departments of the Paris region only cover an area of around 12,000 km2, we mustn't forget the other 130,000 km2 of the Paris Basin in the geological and geomorphological sense of the term - i.e., comprising much more than just the departments of the region. Formed in the Permian period (295 million years ago), the Paris Basin, a sedimentary basin, only really came into being in the Triassic period, during the marine transgression of the Secondary Era, around 245 million years ago. Today, the basin takes the form of a wide basin, raised at the edges and backed by ancient massifs: the Ardennes to the north-east, the Vosges to the east, the Morvan to the south-east, the Massif Central to the south and Brittany (Massif Armoricain) to the west. To the north, the basin remains largely open to the Belgian basin, which is its natural extension.
The four sedimentary plateaus that make up the geological bedrock of today's Île-de-France (Beauce, Brie, Plaine de France and Vexin) revolve around the river funnel concentrated in and around Paris.
The region's landscapes are made up of broad alluvial valleys, buttes crowned with forests and woods, and rich silty openfields - vast tracts of arable land - home to field crops (cereals, weeds, oilseeds, forage) that are among the most productive in the world. Large forests, such as Rambouillet and Fontainebleau, survive on siliceous soils, while rare areas, such as the grassy eastern Brie region, are devoted to livestock farming. The soils are ideal for market gardening and arboriculture, which have flourished in the valleys.
Forests and woods
Although Paris and its immediate surroundings have few forests due to urbanization, the Île-de-France region as a whole has significant forested areas, covering almost 280,000 ha out of a regional surface area of 1,207,000 ha. This represents an afforestation rate of 23%, close to the national average. There are around 12 million trees for a roughly equivalent population, i.e. 80m2 of forest per inhabitant! Ile-de-France forests are mainly made up of hardwoods: oaks, poplars, chestnuts, common ashes, conifers and beeches. Hunting is a traditional activity in the Paris region. There are thousands of deer, roe deer and wild boar, which are more difficult to count. Forests remain important because their biodiversity contributes to the quality of the Île-de-France environment: there is more forest here per square kilometer than in some regions of northern France, for example! Paris is bordered by the Bois de Boulogne (8.50 km2) and the Bois de Vincennes (9.95 km2).
Plateaux and plains
Although it has no marked relief, the region is not without its peculiarities. For example, the Brie region is more of a plateau than a plain. To the east, it extends over a large part of Seine-et-Marne, but also touches on a number of communes in Essonne, Seine-Saint-Denis and Val-de-Marne. It covers around 5,000m2. The eminently agricultural Beauce extends southwards into the Essonne and Yvelines departments of Ile-de-France, starting with the Fontainebleau and Rambouillet forests and extending into Eure-et-Loir and Loir-et-Cher. In the Île-de-France region, the French Vexin extends into the Val-d'Oise and Yvelines, and also covers the Oise; beyond this, it becomes the Vexin Normand. The Plaine de France, or Pays de France, covers roughly the eastern part of Val d'Oise, part of Seine-Saint-Denis and the extreme north-western part of Val-de-Marne. This silty plain is devoted to cereal growing, but is also home to a large part of Paris's northern suburbs and Charles-de-Gaulle airport.
