Climatic conditions form the basic frame for plant growth. Several climatic indicator are commonly used as elements in combined indicators: precipitation and evapotranspiration are main influencing factors of leaching, runoff and erosion. Data on temperature (minimum, maximum or average) are genearly use to estimate pesticide volatilisation and degradation. Data on wind speed and direction can be used to estimate pesticide drift and erosion. Simulation tools therefore take into account climate data, such as monthly avarage temperature and monthly precipitation sums, which can be obtaines from the ‘WorldClim’ database (http://www.worldclim.org) (Hijmans et al., 2005).