A community-driven initiative is amassing data on urban form and function to help cities worldwide to develop their own heat-adaptation plans (see Nature 524, 402–404; 2015). It is called the World Urban Database and Access Portal Tools (WUDAPT; www.wudapt.org).

Urban experts use freely available Landsat satellite imagery to create and study local climate zones across their city (see also B. Wake Nature Clim. Change 2, 487; 2012). Citizen scientists gather information on building materials and function, landscape morphology and vegetation types.

These extensive open-access WUDAPT data will provide a standardized characterization of the world's major cities and detailed input data for urban climate models. City planners and climate modellers will be equipped with accurate boundary conditions for investigating a range of mitigation and adaptation scenarios. Other applications include modelling the effects of changes to the energy infrastructure and improving the assessment of greenhouse-gas emissions through better calculations.