It has been suggested that this article be merged into Drôme. (Discuss) Proposed since December 2012.
The climate of the Drôme department is in a zone of transition between the oceanic climate of Lyon, the continental climate of the north and the Mediterranean climate of Provence to the south. In the Rhône valley, the meeting of mild and humid southern Mediterranean air masses with colder northern air sometimes causes particularly violent thunderstorms and snowstorms. The French Prealps have a very cold mountain climate.
In the hills in the north of the Drôme near Tain-l'Hermitage (15 km north of Valence), the climate is a mixture of oceanic and semi-continental climates. Rainfall occurs throughout the year with the most falling in spring and autumn. The summers are moderated by storms and the mistral does not blow too hard. Saint-Donat-sur-l'Herbasse has a moderate temperature of 3°C in January and 21°C in July due to the Lyonnic climate, where more precipitation falls in summer than winter.
The influence of the mountains is evident in the east. In the Vercors Plateau, the mountain climate is wet due to the oceanic influences from the north. The average annual temperature at Lus la Croix Haute at altitude 1061m is 7.3°C and the annual rainfall is 1051mm. The Diois (southern Vercors) and the Baronnies are dry regions due to the Mediterranean climate. The mistral is less influential here and this region has minimal rainfall. The lowest temperatures in January at Nyons is 0.3°C but 1.4°C at Pierrelatte.
The Valence plane is a transition zone between the Mediterranean influence and the northern cold climate. Summers are colder than in the northern regions, and the increase in sunlight and heat is evident upon the appearance of Mediterranean vegetation in the region. The temperatures are moderate between Lyon and Montélimar. Valence's average temperature in January is 3.8°C and 22°C in July. The mistral here blows heavier.
From Montélimar, the climate can be considered to be that of a Mediterranean climate. Near the highway, the change of vegetation is particularly visible near the stream at Donzère, particularly due to the change of the soil profile. The most southern part of the department clearly exhibits a Méso-Mediterranean climate with the reinforcement of the mistral and a hotter summer due to the rarity of storms. Most rainfall occurs in autumn and the winters are milder than the rest of the Drôme. Pierrelatte an average temperature of 5°C in January and 23°C in July.