"Drought monitoring involves measuring changes in precipitation, temperature, and surface and groundwater supplies, among other factors. Although some drought events (such as flash drought) can emerge relatively quickly, droughts are typically creeping, slowly emerging disasters that can be monitored over time as they develop. Identifying the types of impacts to which a region is vulnerable is important in selecting drought indicators for a particular drought monitoring and early warning process. A drought early warning system can then initiate actions that mitigate the impacts of drought on a community" (World Meteorological Organisation (WMO) and Global Water Partnership (GWP) 2016)
World Meteorological Organisation (WMO), and Global Water Partnership (GWP). 2016. Handbook of Drought Indicators and Indices. Geneva: Integrated Drought Management Programme (IDMP). https://doi.org/10.1201/9781315265551-12.