Chapter 4 examines efforts in the nineteenth and early twentieth centuries to better understand Britain’s rain. Meteorologists had attempted to investigate the distribution of rain prior to the 1850s, but observation points remained few and inadequately distributed. The solution to answering questions about the geographies of the rain was the establishment of a rainfall observatory network that covered the entirety of the British Isles. The network of rainfall observing stations was established by George Symons and became known as the British Rainfall Organisation. It relied almost exclusively on volunteer labour. The first section of the chapter details the early years of Symons’s Rainfall Organisation and its key administrative features, before moving on to discussions about rain gauges and station exposures. The chapter then examines a series of experimental trials that ran from 1863 to 1890 and discusses the ensuing controversy regarding the value of the experiments and of the observatory network more generally. The chapter then looks at contemporary discussions about the value of various statistical treatments of rain data, before finishing with Alexander Buchan’s and Hugh Robert Mill’s rainfall maps and the maps’ contributions to data management and public utility.