Humidity during the vegetation period
Map showing the humidity during the growing season: < -50, very dry; -50 - 0 dry; 0-50 weakly humid; 50-100 humid; 100-150 strongly humid; 150-200 very strongly humid; > 200 very strongly humid.
Areas where the addition of water from rain is larger, than the loss of water from evaporation and transpiration are denoted humid. For plants, humidity is crucial to the risk of encountering water deficiency. During winter plants in principle use no water, and thus are independent of the amount of precipitation. Humidity is therefore most important during the growing season.
Maximum humidity is found in areas with a large amount of precipitation and low temperatures, that is in the northern and western parts of Sweden. Normally the amount of precipitation is less and temperatures are higher in the eastern parts of Sweden, resulting in lower humidity. During the growing season humidity often is negative, and the deficiency of water arising during summer must be restored during winter. Dry periods are therefore most common in the eastern parts of Sweden, although the western parts sometimes also are subjected to drought resulting in serious damages because trees are not adopted to water deficiency.