2025's flood events illustrate the accelerating trend of hydrological intensification driven by ongoing global warming.[1] A preliminary global review (Figure 1) shows extreme and often record-breaking rainfall on every continent, with many events producing exceptional sub-daily intensities. Crucially, severe flooding is increasingly occurring in locations not historically classified as high risk, prompting renewed scrutiny of exposure and preparedness.
Recent flooding illustrates how once-in-a-lifetime events are now occurring in rapid succession. The United States’ Texas Hill Country floods, with more than 500 millimeters of rainfall in two days, exemplified this shift, resulting in substantial loss of life and revealing gaps in emergency response and insurance coverage. Further evidence of this intensification has been seen in Pakistan, Spain and elsewhere. The persistence and clustering of such extremes align with trends clearly established in 2023[2] and 2024.[3] Climate change is increasing rainfall intensity and expanding flood hazard footprints, while societal exposure continues to outpace preparedness.
Flood impacts arise from three principal mechanisms: 1) fluvial flooding, when rivers exceed capacity and inundate surrounding land; 2) coastal flooding, when tides, low-pressure systems and wind-driven surge raise sea levels; and 3) pluvial flooding, when intense rainfall overwhelms drainage capacity.
While riverine and coastal floods dominate public perception, pluvial floods are a major and growing source of damage. In Britain 6.3 million homes are thought to be at risk of flooding from all sources. Of these, 4.6 million or 73% are at risk from pluvial flooding.[4] According to the Federal Emergency Management Agency (FEMA), in the United States the proportions at risk from the three main flood mechanisms are very similar.[5] In continental Europe, France, Germany and Poland are dominated by fluvial flood risk, but pluvial flooding is the fastest rising driver.
In the U.S., FEMA produces flood maps, which are used to underpin many risk management activities including administration of the National Flood Insurance Program (NFIP). One of the mapped flood extents is the Special Flood Hazard Area (SFHA) which delineate the 1-in-100-year flood outline. However, all but the most recent versions of these maps do not account for pluvial flooding. Pluvial flood risk is more difficult to map than fluvial or coastal flooding because it can occur far from rivers or coastlines and requires precise elevation data and knowledge of drainage capacity. The largest uncertainty stems from estimating intense rainfall: long-term rainfall records on which this assessment is based are often limited and climate change makes the problem a moving target. Consequently, many countries have been slow to develop or publish pluvial flood maps, leaving significant gaps in risk assessment and planning.
According to a recent study led by the University of Michigan,[6] in the United States, pluvial claims typically result in smaller individual payouts than catastrophic river floods (median damage is about $9,500 per claim versus $51,000 for major events) but their sheer frequency makes them costly in aggregate. In lower risk areas outside SFHAs, pluvial flooding accounts for most claims and casualties. The same study reported that 87% of claims from properties outside FEMA’s SFHAs were due to pluvial flooding. Between 1978 and 2021, the NFIP paid $4 billion for pluvial flood claims outside of the SFHA, compared to $2.3 billion for major river floods in the same zones. These figures exclude uninsured losses, which are likely several times higher.
Extreme weather is not just a future concern — it is today’s operational reality. Businesses that fail to adapt will face escalating losses, supply chain disruptions and reputational damage. Here are practical steps to strengthen resilience:
Climate projections indicate that hydrological extremes will intensify, with convective storms delivering rainfall rates far beyond historical norms even in areas with no historical flood record. A new partnership including Willis and Newcastle University, the EXTREME-FUTURES initiative, will combine advanced climate science and AI to improve forecasting and resilience strategies. In the interim, businesses cannot afford complacency. Risk managers must recognize that pluvial flooding now accounts for much of the flood risk in many regions — and that traditional flood maps do not always capture this threat.
