Extreme weather events, including floods and droughts, occur increasingly often. They affect the operational efficiency and sustainability of water supply, drainage and sewerage infrastructure, and wastewater treatment services, and threaten their protection of public health and the environment. The guidance in this publication summarizes how basic disaster preparedness and early warning procedures can be implemented in the water and wastewater sector, and identifies the specific challenges of extreme weather events to vulnerable areas. It provides advice on the implementation of water safety plans as a tool for risk assessment and management, giving specific attention to smallscale water supply and sanitation systems; and on multisector cooperation, including communication. Finally, based on a review of experience and good practice in the European Region, it summarizes proven adaptation measures for water utilities, drainage and sewerage, and wastewater treatment systems during extreme weather events.