A numerical computer simulation has been developed for the electrostatic spray paint process. The theoretical model describes the path of a cloud of charged drops. It takes into account the drop size, temperature, density, viscosity of paint and air, charge of the drops, potential of the sprayer head, the use of air assistance, air-paint ratio, paint flow, wind and turbulence and the distance towards the object. Especially the influence of the wind and wind turbulence on the spraying process was investigated. With increasing crosswind a higher charge, larger drops or air-assisted spraying will keep the efficiency high. Too much charge on the drops will cause the cloud to expand too much. Painting in the open air with a mild wind is possible using the electrostatic spray paint process.