This article uses diatoms and the role they play in cloud formation as a prompt to consider histories of weather modification in practice, science fiction and possible future applications to address climate change. Diatoms are a form of microalgae that are present in all waterways and contribute significantly to atmospheric oxygen. They also provide condensation nuclei around which water droplets form, effectively creating clouds. Such naturally occurring particulate matter interacts with intentional and unintentional anthropogenic influence on the atmosphere. The long history of folk speculation and scientific experimentation about effective ways of seeding clouds for rain can help us consider the potential impacts of new forms of atmospheric intervention. From the use of algae as a tool for bioremediation to marine cloud brightening techniques, a multiscalar ecological awareness needs to be publicly fostered in making choices about how to influence climate futures.