Preparedness towards natural hazards is a key factor in the reduction of their impact on the society. Recent international initiatives are fostering the development of a culture of risk prevention and the promotion of early warning systems. Numerical weather predictions have become the basis of several flood-related warning systems, enabling the detection of hazardous events with sufficient lead-time to prepare effective emergency and response plans. The objective of this paper is to review current European operational warning systems for water-related hazards induced by severe weather conditions. In details, it includes systems for detecting surface water flooding, flash floods, debris flows, mud flows, rainfall-induced landslides, river floods and coastal floods. Technical features and capabilities of different systems are described, together with some noteworthy examples. The main strengths of each system type are highlighted and suggestions are provided for developing and further improving their overall skills in hazard detection and the mutual coordination.