 During the 1962 July – August storm season in Flagstaff , Arizona , the scientists , selected " guinea pig " storms , and seeded them with chemicals . Effects were thoroughly analyzed from the ground and from the air with time @-@ lapse motion picture cameras , stereo still cameras , storm radar , lightning detectors , and airborne heat sensors . Among the agents inserted in selected clouds were " condensation nuclei " which temporarily increased the number of water droplets in the cloud , and pulverized dry ice , which turns a portion of the cloud to fine snow crystals that remain aloft . The utilization of these agents facilitated study of a storm 's characteristics . 
