Sufficient rainfall (450 - 500 mm) is necessary to the vine primarily to keep its cells from collapsing (causing wilting) which prevents them fulfilling their vital functions. Some water-stress during berry maturation may improve the quality of the crop, but severe stress is detrimental as it halts vegetative growth and will cause leaf loss.

In England, drought is a problem on very young vines and in exceptional years in very shallow or free-draining sites. In fact, the availability of rainfall to the plant depends very much on the soil type and the season and rate at which it falls.

The best areas for vinegrowing in England are those with low rainfall, as excess rain will:

• Cool the climate
• Make it more difficult to pass machinery in the vineyard.
• Increase the risk of fungal disease; especially mildews, grey rot and Phomopsis.
• Reduce fruit set, especially if accompanied by low temperatures.
• Cause bunch compaction and eventually berry splitting prior to harvest
• Dilute the must if it rains just before harvest.

High winter rainfall has little effect on vine growth, but some water is stored for later use. Moderate spring rain is beneficial, as it promotes shoot growth. Some summer rain is useful, but this can encourage disease and reduce fruit set. Autumn rain is nearly always detrimental to the quality of the crop