The dirunal temperature range is the difference between the daily maximum temperature and nightly minimum temperature in one day of a vineyard.
A vineyard with a high diurnal temperature range is thought to be important in quality viticulture.
In warm or hot climates, high daytime temperatures result in high sugar levels in grapes. The shift to cooler temperatures at night helps to cool the grapes at night therfore maintaining the acidity levels in grapes. The resultant wines are ripe and refreshing at the same time.
In cool climates, a high diurnal temperature range helps to increase the colour, flavour and aroma development in grapes.