Knowing what the weather will do: A guide for practitioners on impact-based early warning
This guide introduces a novel framework and step-by-step methodology for developing impact-based early warning (IbEW) systems that move beyond forecasting “what the weather will be” to anticipating “what the weather will do” — the actual impacts of hazards on people, livelihoods, and assets. Aimed at governmental and non-governmental organizations engaged in early warning, disaster risk management, humanitarian response, and early action, it shows practitioners how to integrate risk knowledge — exposure and vulnerability information — with hazard forecasts to produce warnings that are timely, targeted, and actionable. The approach builds on the IPCC risk framework, treating risk as the dynamic interaction of hazards, exposure, and vulnerability, with particular attention to how impacts fall disproportionately on vulnerable groups such as women and girls, persons with disabilities, and people in displacement settings.
The methodology is organized into four practical modules: needs assessment (mapping existing systems, defining scale and users, and establishing inclusive co-production), building risk knowledge (selecting hazards and vulnerability profiles and co-developing conceptual “impact chain” models), translating concepts to data (selecting and validating indicators, sourcing and harmonizing datasets, and building automated workflows), and operationalization and communication (visualization, validation, capacity-building, and reflecting on limitations). Each module pairs clear steps and guiding questions with a self-assessment checklist for practitioners.
A concrete application example runs throughout, drawn from the EarlyWarning4IGAD project, which piloted the approach in Kenya for two priority risks: crop loss for subsistence farmers in rain-fed agricultural systems due to drought, and physical harm to people due to floods. The example details real implementation choices — using the Combined Drought Indicator with crop calendars and the FloodPROOFS hydrological model, harmonizing population and vulnerability data, and publishing outputs on the East Africa Drought Watch and East Africa Flood Watch platforms hosted by IGAD’s Climate Prediction and Applications Centre (ICPAC). Produced by UNU-EHS in collaboration with ICPAC, RCMRD, and CIMA Research Foundation and funded through UNDRR, the guide is a practical resource for anyone working to transition hazard-based early warning systems toward impact-based, people-centered warnings.