This article examines the most controversial of the activities of the India Meteorological Department : long-term seasonal forecasting for the South Asian subcontinent. Under the pressure of recurrent famines, in 1886 the imperial IMD commenced annual issue of monsoon predictions several months in advance, focused on one variable: rainfall. This state service was new to global late nineteenth-century meteorology, attempted first and most rigorously in India. Successive IMD leaders adapted the forecast in light of scientific and infrastructural developments, continuously revising (...) the underlying methods of its production. All methods failed to achieve accurate prevision. Nevertheless, the imperatives of economic administration, empire and public demand compelled IMD scientists to continue annual publication of this unreliable product. This article contends that the seasonal forecast is best understood as an enduring ritual of good governance in a monsoonal environment. Through analysis of newspaper controversies, it suggests that although the seasonal forecast was the most compelling justification for the IMD's imperial and global importance, its limitations undercut popular trust in modern meteorology. Finally, this case illustrates the centrality of ‘tropical meteorology’ to the historical development of modern atmospheric science. (shrink)