How is a warm climate defined in terms of Growing Season Temperature (GST)?

• A. Regions with an average GST of 18.5-21°C (65-70°F)
• B. Regions with an average GST in excess of 21°C (70°F)
• C. A measure of the difference between the annual mean temperatures of the hottest and coldest months
• D. The mean temperature of the entire calendar year

Answer: (A)

Growing Season Temperature is the average temperature during the months when grapes are actively growing. A warm climate is defined by an average GST in the range of 18.5–21°C (65–70°F). This level of warmth provides enough heat for steady ripening while maintaining enough acidity and structure; it’s warmer than cool-climate ranges but not so hot that sugar accumulates too quickly or acidity drops too much.

The other descriptions refer to different climatic measures: a large temperature difference between the hottest and coldest months describes thermal amplitude, not GST; the mean temperature of the entire calendar year is the annual mean, not the growing-season value; and GST above 21°C would indicate a hot climate, not the warm category.