Cloud Behavior is a study of clouds through photographs, drawings, essays, and interviews. During summer 2018, Nanna Debois Buhl photographed clouds on medium-format film and experimented with the images in the darkroom. Buhl's cloud photographs connect to historical thinking about clouds, to scientific research on cloud behaviour, and to the mystical and meteorological contemplation of clouds by August Strindberg. Today, climate researchers study cloud behaviour to understand how global warming affects the movements of clouds and how, conversely, the movements of clouds might affect global warming. Strindberg and climate researchers share an interest in reading signs and omens in the clouds – and do so with the aid of photography and other means of visualization. This connection is unfolded in various ways in the texts of the book.