The risk of extreme water shortages due to climate change is predicted to affect almost three-quarters (74%) of drought-prone regions by 2100, according to research published in Nature Communications. A prolonged lack of rainfall, reduced river flow and reservoir levels, and increased water usage all contribute to extreme water scarcity events, also known as ‘Day Zero Drought’ (DZD) events. Although it is well established that climate change will affect water systems across many regions, it is currently unknown when and where severe water shortages will occur and therefore the ability to plan for water scarcity is limited. Almost 35% of these regions may face severe water scarcity between 2020 and 2030. The authors call for the development of proactive policies to address the risks of climate change and unsustainable water use.