Cloud Seeding Against the 1964 Drought in the Northeast

Abstract

A short account is given of seven cloud-seeding programs conducted in the summer and autumn of 1964 for drought relief in the Northeast, and evaluations of six of them by target-control regressions of normalized monthly data are presented. The results indicate increases varying from one to sixty per cent, averaging twenty-five per cent, nominally significant at the one per cent level. Circumstances such as non-randomization that compromise the evaluation are discussed. Note is also taken of an indicated fourteen per cent rainfall increase in 1964 in a hail-suppression target area where operations were recently suspended on account of a state law prohibiting cloud seeding on the grounds that it contributes to drought.