photo of a cell phone tower rising above a field and some treesFor the American Physical Society’s Physics magazine, Rachel Berkowitz explains how cellular networks can offer critical rainfall data to the smallholder farmers across Africa who feed most of the continent but lack access to weather-prediction systems used in wealthier regions. Hydrologists have proved that average rainfall along the path between towers can be derived by measuring changes in the quality of electromagnetic signals at a receiving tower, since the signals are attenuated by rain at a predictable rate. Researchers are now working to unlock this data for the countries that need it. Photo by Corey Coyle via Wikimedia Commons