For many, summer means long sunny days, warm evenings, and relaxed moments with a glass of wine: terrace dinners, a chilled bottle of sparkling wine, rosé, or a fruity white. But in wine regions, summer weather is viewed through a different lens. While sunshine and warmth are essential for grape ripening, the increasingly frequent combination of prolonged drought and heat poses serious challenges for growers and winemakers.

At first glance, hot summers seem ideal: abundant light boosts photosynthesis, accelerates sugar accumulation, and intensifies grape aromatics. But there’s a tipping point—when favorable becomes excessive. Without adequate rainfall, which has become more common in recent years, vines eventually experience water stress. The upper layers of the soil dry out rapidly, especially if winter and spring were already lacking in precipitation. As a result, roots struggle to access enough water and nutrients.

Rosé wine can be well-deserved joy in summer

Drought during flowering is especially critical. This is the stage when fruit set is determined—how much yield will develop and how compact the grape clusters will be. High temperatures and dryness during flowering can lead to poor fruit set, resulting in fewer and smaller berries. While this may reduce yield, it can also create interesting opportunities from a quality perspective.

Grapevines respond wisely: when they sense water stress, they slow down vegetative growth and shift focus to ripening. This is a natural response, but if the dry period is prolonged, it can disrupt ripening itself. Berry development slows, acids degrade more rapidly, and sugar levels may rise too fast. This imbalance can lead to wines that taste flatter, less vibrant, and lacking in freshness.

At this point, vineyard management becomes a delicate balancing act. Growers aim to open up the fruit zone for better airflow, to prevent berry overheating, while also staying vigilant about disease control. Although dry, hot conditions suppress fungal diseases like downy mildew or botrytis, powdery mildew remains a threat—especially in grape varieties with dense canopies.

However, not all grape varieties respond the same way to heat and drought. In general, deep-rooted and thick-skinned varieties are more resilient, while thin-skinned, early-ripening ones tend to be more sensitive. For example, Kékfrankos (Blaufränkisch) adapts relatively well to heat and has proven itself even in drought years in Hungary. Cabernet Sauvignon is another survivor—its thick skin and long ripening period make it less vulnerable in hot weather. Among white grapes, Olaszrizling (Welschriesling) and Hárslevelű show stable performance, while Rieslingszilváni and Cserszegi Fűszeres tend to be more reactive, ripening too early or losing acidity quickly under stress.

Cabernet Sauvignon grapes nearing full ripeness

Pinot Noir, in contrast, is particularly delicate. Its thin skin makes it prone to sunburn, and its fast sugar accumulation makes it hard to preserve freshness in long hot summers. This sensitivity also applies to red grapes intended for rosé production, where preserving the bright fruit character and crisp acidity is key—conditions best supported by a more balanced climate.

Ultimately, the type of wine a hot and dry summer yields depends largely on how the weather evolves. If some rainfall arrives in mid- or late summer, vines can regain balance and still produce aromatic, concentrated, age-worthy wines, even from smaller clusters. If drought persists, however, yields will shrink and the vintage will take on a different character—often with higher alcohol and a bolder profile. That’s why we’re increasingly seeing white wines with alcohol levels of 14.0–15.0%, instead of the traditional 11.0–13.0%.

Sunny vineyard in Tuscany

The experience of recent years, including the extreme heatwaves of early summer 2025, reminds us that climate change is no longer a distant theory—it’s part of the everyday reality in wine regions. Grapes love the sun, but even good things can be overdone. For winemakers, the challenge is to find balance in every vintage—something that now requires not only expertise, but also flexibility and foresight.