In late July most grape varieties start to enter the ripening phase of their growth. This is often defined narrowly with the French term veraison. In July, the start of the ripening phase is often visibly, and more roughly, described as the time when the grape berries start to change color.
Of course, not all varieties actually do show a distinct color change as they ripen. Many white wines are more subtle in the ripening, only detectable by taste (the historical method) or chemical analysis. Later in the year, such white wine varieties’ most noticeable change will be a swelling of the berries in size, and the berries will become more translucent.
Ripening is affected by many factors. This year has been extremely dry and hot. In such hot and dry conditions the grapes can reach ripeness too quickly, which means they do not have sufficient time to fully mature on the vine (called the hang time) before they need to be harvested; which of course affects the resulting wine. The total environmental contributions are complex, and so the results are often variable, either producing only a moderate quality wine or possibly one of exceptional character. And only time will tell what this year’s harvest will generate.