Suitability of a region for viticulture, which can be measured by objective criteria. Important criteria are climate and weather, which are eminently important for the thriving of the vines in the course of the vegetation cycle. The exposure (direction of sunlight) or orientation of the vine rows plays an extremely important role, whereby a slope location with a corresponding inclination positively enhances the effect. In warmth-favoured, dry areas, south-east to east-facing slopes are optimal, in climatic border areas with heat deficits but sufficient precipitation, south to south-west exposures are optimal. According to research in Geisenheim, the optimal temperature for vine growth is between 25 and 28 °C. Towards the end of the ripening full stop, it should be between 15 and 20 °C to achieve optimal physiological ripeness of the grapes. Sunny days alternating with cooler nights are advantageous with regard to the balance of sugar and acidity. Shortly before the grape harvest, heavy rainfall is undesirable because of the risk of watering.