Vitis vinifera (the common vine) adapts to everything and tolerates almost everything: it recovers after periods of drought, very hot summers, frosts ... but there is a limit to the cold beyond which, when the buds appear, serious damage can occur. This limit is -15°C: therefore we are not talking about spring frosts, but about a prolonged freezing climate, however,
a rather rare event. In any case, at -10°C the problems for white berried grapes begin. It should be considered that with very low temperatures the greatest damage occurs in the valley, because the hills and the foothills enjoy the temperature range. The vine needs adequate heat, in correspondence with each vegetative phase.
From 8 to 13°C the vine sprouts, and from 16 to 20°C the vine blooms. Finally, temperatures above 18°C and below 24°C are required for the grapes to ripen. The process of the grapes ripening is influenced by the quantity of light, which in cool summers can compensate for the lack of heat, and the deep winter rest, with the prolonged action of the cold which naturally favors the elimination of fungi and parasites.
As regards rainfall, which plays a fundamental role in grape production and in terms of grape quality, the period most feared by winemakers corresponds to spring. The ancient wisdom summarizes in the rule of three tens the ideal condition for the development of attacks of peronospera, a dangerous cryptogamic disease of the vine: shoots of 10cm in length added to temperatures of 10°C and the fall of 10mm of rain open the doors to the disease. We therefore deduce that the rains are welcome in winter and before the spring temperature reaches 10°C. Furthermore, rain is not good for the vine flowering and is not welcome even at the time of harvest, when it can cause the onset of mold and rot.
In case of drought, those who want quality grapes production do not resort to irrigation unless it is an extreme emergency. It is good to remember that particular climates, obviously in conjunction with other factors, correspond to particular wines such as Marsala in Sicily or Vermentino in Sardinia - which are obtained from historically acclimatized vines in these areas. With respect to these, certain areas are considered privileged that enjoy the thermoregulation due to lakes and rivers. The microclimate generated by these geographic elements intervenes in the modification of the layer of air that surrounds the vineyard (the phenomenon affects two meters of air from the ground). The cultivation of the vineyard itself determines significant changes in the microclimate, therefore rational pruning interventions on the vine, good drainage, right exposure, planting distances, etc. directly affect the crop.
Around the large Italian lakes, such as that of Garda -North-West from Verona-, for example, a temperate and dry microclimate is created which, combined with the fertility of the soil, allows the development of luxuriant vineyards and the production of excellent wines.
Source: Edizioni Del Balbo - Enologia, Vite