An analysis of five decades' worth of data finds that climate change is altering the timing of river flooding across Europe. The results reveal that rivers are flooding earlier in the spring in the western and northeastern regions of the continent, and later in the season around the North Sea and some sectors of the Mediterranean coast. River flooding affects more people worldwide than any other natural hazard, with an estimated global annual average loss of US$104 billion. Such costs are expected to increase as a result of continued economic growth and climate change. Here, Günter Blöschl and colleagues analyzed data collected from more than 4,200 hydrometric stations in 38 European countries between 1960 and 2010. As well, they compared precipitation, soil moisture and temperature data to explore potential drivers of flood changes. The most substantial changes occurred in western Europe along the North Atlantic coast from Portugal to England, where 50% of the stations recorded a shift toward earlier floods by at least 15 days over the 50-year period; the authors attribute this shift largely to the nature of soil (in particular, its ability to retain moisture) in this region. Nearly all stations in northeastern Europe recorded a shift to earlier flooding as well, with about half finding the shift to exceed eight days; these changes are largely due to increases in snowmelt that occur in a warmer climate. Around the North Sea, about half of the stations recorded a shift toward later flooding by more than eight days, which the authors attribute to extreme precipitation occurring during the winter and changes in the North Atlantic Oscillation. In a related Perspective, Louise J. Slater and Robert L. Wilby note, "Without adaptations, such changes in flood seasonality can profoundly affect agricultural yields, infrastructure safety and operation, hydropower production, water supplies, and water management. The study thus prompts important questions about flood predictability."