The submountain plateau where Fos vineyards are located has a marked inland Mediterranean nature: a temperate climate where winters are cold and summers are hot and dry, and where the average rainfall does not exceed 400mm per year—reaching its maximum during spring—, mainly due to the Foehn effect caused by the Sierra de Cantabria, north of Elciego, which limits the wet and cold influence of the Cantabrian Sea.
Average temperatures and rainfall
The «average daily maximum» (solid blue line) displays the average maximum temperature of one day for each month. Likewise, the «average daily minimum» (solid ochre line) displays the average minimum temperature. Hot days and cold nights (blue and ochre dotted lines) display the average temperature of the hottest day and the coldest night of each month for the last 30 years.
The maximum temperature diagram for Trus shows how many days a month certain temperatures are reached.
The precipitation diagram for Elciego shows how many days a month certain amounts of precipitation are reached.
Cloudy sky, sun, and rainy days
The graph shows the monthly number of sunny, partly cloudy, overcast, and rainy days. Days with less than 20% of clouds are classified as sunny days; days with 20-80% of clouds, as partially cloudy; and days with more than 80% of clouds, as cloudy.
Elciego chart shows how many days per month the wind reaches a certain speed.
The Wind rose displays the number of hours per year where wind blows in the indicated direction.
Temperature and water availability are the most important climate elements for the vineyard’s development.
A prolonged period of mild temperatures is required to achieve ripeness.
The metabolic development of the vineyard begins with temperatures above 10°C and carries out its cycle of photosynthesis with average temperatures between 15° and 30°C. A significant difference in temperature between summer and winter allows the vineyard to enter a state of rest. The plant stops the ripening process with temperatures above 35°, while winter frosts below -15° may kill it. Temperature variations between day and night (thermal amplitude) also significantly affect how grapes ripen. If there is little variation, grapes will lack acidity; while if the difference is significant, grapes will be better balanced and will retain acidity.
It should be noted that every 100 meters above sea level the average temperature is reduced by approximately 0.6°C, and that planting on a hill with a certain orientation reduces vineyards’ sun exposure (sunshine is another key element, since it is the driving force of photosynthesis).
The orientation of both the vineyard and the vine rows, as well as the distance among them, the different pruning systems and the leaf mass treatment to increase or reduce exposure and aeration of bunches, are key elements aimed at optimizing the sunlight effects. These decisions will depend on the varieties planted, as each variety has different vigor and growth patterns.
The most relevant aspect of vineyard rainfall is not the volume of the rainfall itself but the moment of the growth cycle when it takes places, as there are wine-growing areas with very high or very low rainfall. Winter rainfall helps create water storage; rainfalls at the beginning of the growth cycle can affect the harvest size, while rainfalls before harvest can influence quality by diluting sugars and acids, as well as breaking the aromatic balance of the grapes. The most feared consequence of rain is the risk of fungal diseases that can quickly spread through the vineyard and ruin the harvest.
In some areas, there are always autumn rains. The only uncertainty is when will it rain. Every year, winegrowers have to take the risk of deciding between obtaining greater ripeness or having their harvest ruined by rain. Grapes grown in colder climate vineyards and with longer ripeness periods have more complex and interesting aromas, and that will be transferred to the wines.
The most interesting and sought-after wines come from areas with marginal climates for the grown varieties, even though achieving complete maturation may be more difficult.
Since different grape varieties have different ripening paces, it is very important for winegrowers to decide what varieties they will plant in their vineyards. In all climates, there are a series of varieties that ripen more easily, while others are more challenging. However, it is important to bear in mind that some varieties are more tolerant to climatic extremes. Some varieties ripen in an average temperature range higher than that other types, which only reach optimum ripeness in a narrow range of temperatures.