Climate zones and USDA zones in France

Map of climates in France + USDA zones

USDA hardiness zones

The USDA zones concept is American, it was created by the United States Department of Agriculture (U.S. Department of Agriculture, hence the USDA name). It is a geographical division into 26 isothermal zones based on the average of minimum temperatures over the past 20 years. Concretely, these indicators express the “likely minimum temperature” your region will experience in winter, which is fundamental when discussing hardiness!

This way of approaching hardiness zones is used in many countries, including France. USDA zones have the advantage of being fairly precise and are widely used worldwide. The scale comprises 26 steps but in France only 10 are used, from zone 6a to zone 10b.

Summary table:

Type 1: mountain climates - USDA Zone 6a

Mountain climates are quite varied and found throughout almost all of France: Pyrenees, Massif Central, Alps, Jura, Morvan, Ardennes but also, at lower altitudes, the plateaux to the east of Champagne and part of Lorraine and Franche-Comté…

In these geographical areas, the following are observed:

• a high number of days and high total precipitation (rain, snow…)
• a mean temperature below 9.4°C with more than 25 days during which minimum temperature was below -5°C and fewer than 4 days with maximum above 30°C.
• Interannual variability of July precipitation and winter and summer temperatures is greatest.

→ This climate corresponds to USDA zone 6a (recorded minimum temperatures: -23.3 to -20.6°C)

Type 2: semi-continental climate and climate of montane margins - USDA Zone 6b

Type 2 climate is intermediate between mountain climates and types 3, 4 and 8. The area affected by this climate comprises the montane peripheries and extends over large parts of Burgundy, Lorraine and Alsace.

In these areas :

• temperatures are milder than in mountain climates (but, at equal altitude, colder than elsewhere),
• precipitation is slightly lower and less frequent,
• there is a low autumn-to-summer precipitation ratio

→ This climate corresponds to USDA zone 6b (observed minimum temperatures: -20.6 to -17.8°C)

Type 3: degraded oceanic climate of central and northern plains - USDA Zone 7a

Type 3 climate covers the whole Paris Basin with an extension to the south (middle Loire Valley, northern Massif Central and Saône Valley).

Climate remains oceanic but with marked variations :

• Temperatures are intermediate (mean annual temperature around 11°C, 8 to 14 days per year with temperatures below -5°C).
• Precipitation is low (less than 700 mm annually), especially in summer, but rainfall occurs on average on 12 days in January and on 8 days in July, values averaged for France as a whole.
• Interannual variability of precipitation is low while that of temperatures is high.

→ This climate corresponds to USDA zone 7a (observed minimum temperatures: -17.8 to -15°C)

Type 4: Altered oceanic climate - USDA zone 7b

Type 4, altered oceanic climate appears as a transition between true oceanic (type 5) and degraded oceanic (type 3). Between Nord-Pas-de-Calais and Normandy, it forms a narrow strip while to the west this transition widens to more than 150 km. This climate also affects the south-west of the Massif Central, from Dordogne to Aveyron and the northern Pyrenees.

Les caractéristiques :

• Mean annual temperature is relatively high (12.5°C) with a low number of cold days (4–8 per year) and a sustained number of hot days (15–23 per year).
• Annual temperature range (July–January) is near the minimum and interannual variability is average.
• Precipitation, average annual total (800–900 mm), falls mainly in winter, with fairly dry summers.

→ This climate corresponds to USDA zone 7b (observed minimum temperatures: -15 to -12.2°C)

Type 5: Oceanic climate - USDA Zones 8a and 8b

Oceanic climate occupies a narrow strip along the North Sea coast and all of Normandy, Brittany, Vendée and the Charentes. A small oceanic area occurs in western Landes and Pyrénées-Atlantiques.

In these areas :

• temperatures are moderate and very isothermal: annual range (less than 13°C difference between July and January), number of cold days (fewer than 4) and hot days (fewer than 4) and interannual variability are minimal.
• precipitation is abundant annually (just over 1000 mm) and frequent in winter (more than 13 days in January).
• summer is also rainy (8–9 days in July) but totals are low.
• finally, oceanic climate is characterised by strong interannual variation in winter precipitation.

→ This climate corresponds to USDA zones 8a and 8b (observed minimum temperatures: -12.2 °C to -6.7 °C)

Type 6: Altered Mediterranean climate - USDA zone 9a

Altered Mediterranean climate mainly extends over the southern Alps and Pre-Alps, encompassing most of the two departments Alpes-de-Haute-Provence and Drôme. Small remnants can also be found on the left bank of the Rhône around Ardèche and as a narrow strip to the west, between Pyrénées-Orientales and Hérault.

Characteristics :

• annual mean temperature is high, with few cold days and 15 to 23 hot days per year.
• minimal interannual variability in July minimum temperatures: summer is consistently hot year after year.
• annual precipitation total is medium (800–950 mm) but not evenly distributed.
• autumn and winter, wet and highly variable from year to year, contrast with summer, dry and stable relative to 1971–2000 normal.

→ This climate corresponds to USDA zone 9a (observed minimum temperatures: -6.7 to -3.9°C)

Type 7: Climate of the Southwest Basin - USDA Zone 9b

This type of climate applies to a geographically disparate area, straddling several regions (Aquitaine, Languedoc) and centred on the mid-Garonne basin, referred to, for convenience, as the ‘South-West Basin’.

It is characterised by:

• a high mean annual temperature (above 13°C) and a high number (> 23) of hot days, while days with frost below -5°C are rare.
• a large annual temperature range (15 to 16°C) and low interannual variability of winter and summer temperatures.
• Precipitation is not abundant in annual total (less than 800 mm) and in winter; it is somewhat higher during summer. It occurs more frequently in winter (9–11 days) than in summer (fewer than 6 days). This distribution indicates that precipitation intensity is low in winter (oceanic rainfall) and higher in summer (thunderstorm systems originating from Spain or the Bay of Biscay). Interannual variability of precipitation is moderate.

→ This climate corresponds to USDA zone 9b (observed minimum temperatures: -3.9 to -1.1°C)

Type 8: True Mediterranean climate - USDA zones 10a and 10b

This climate occupies a strip of just under a hundred kilometres along the Mediterranean Sea, from the Pyrenees to the Var. Beyond that, in the Maritime Alps the Mediterranean climate narrows so much that it finally appears only sporadically within the alpine valleys.

Climatic characteristics are very distinct, more so than in any of the seven preceding climates.

• annual temperatures are high, cold days are extremely rare and hot days frequent.
• interannual range is large (more than 17°C between July and January) while these characteristics are very stable from year to year.
• the very high ratio between autumn and summer precipitation (> 6) is the main feature of this climate. Annual precipitation total is low with an arid summer but a fairly well‑watered winter despite a low number of days of rain. These characteristics are also stable from year to year.

→ This climate corresponds to USDA zones 10a and 10b (observed minimum temperatures: -1°C to +4.4°C)

To find out more

Discover our advice sheet: Hardy plants and hardiness.