Too much rain? Quite often people see wet winters as a possible sign of a lesser quality vintage. Some people also consider drought years to be the best years. It always depends on the micro climate in the area the vineyard is in. If the vineyard is in the mountains on a hillside or on the valley floor. Each one requires a different technique to control the vigor of the vine. Controlling vigor on the valley floor can start with the use of cover crops in the rows to compete with the vine for the water in the soil.
During a wet season, the cover crop can be left in the rows for a longer period and just mowed. For a moderate season, you can mow one row and till the other. In a year with less rainfall where the vine might struggle you can till all the rows limiting the stress on the vine. Drought years can have their issues as well. Controlling vine vigor and vine stress is an important thing.