Which factor directly influences the diurnal temperature range experienced by vines?

• A. Altitude
• B. Latitude
• C. Proximity to water
• D. Wind

Answer: (A)

Diurnal temperature range is the difference between the day's highest temperature and the night's lowest temperature. What directly drives this swing is how quickly heat is gained during the day and lost after sunset. At higher altitudes, the air is thinner and skies are often clearer, so heat escapes from the ground to the night sky more rapidly. That rapid radiative cooling cools the nights considerably while daytime heating can still reach high values under strong sunlight, producing a larger day-to-night gap. So altitude inherently magnifies the diurnal swing vines experience.

Proximity to water and wind can influence this range in practice—water bodies tend to moderate temperatures, and wind can mix air to reduce extremes—but they don’t control the fundamental rate of heat loss at night as directly as altitude does. Latitude shifts the overall climate but the core day-to-night swing is most strongly tied to altitude in many vineyard settings.