Abstract: A planetary weather modification system comprises a plurality of solar powered unmanned aerial vehicles (UAVs) in communication via a communication network. The UAVs receive a flight instruction to fly in close proximity so as to block the light emanating from the Sun and casting a shadow on the surface of the Earth. The UAVs may fly in circular formation, elliptical formation, rectangular formation, or a vertical column formation. The number of the plurality of the UAVs maybe large enough so as to affect the temperature within an umbral diameter of the shadow so cast on the surface of the Earth.