Climate change is increasing property losses across the Nordic region, but the biggest driver of insured losses is not windstorms or wildfires, but water damage caused by increasingly intense cloudbursts. These events are putting growing pressure on ageing drainage infrastructure and driving a rising volume of insurance claims.
On 17 August 2021, more than 160 millimetres of rain fell in a single day in Gävle, a municipality of around 100,000 people on Sweden’s east coast – more than the town normally receives in two months. Basements flooded, roads closed, and thousands of property owners filed claims. When the industry body Insurance Sweden (Svensk Försäkring) closed the year’s accounts, Swedish insurers had paid out roughly EUR 245 million for natural-peril claims, making 2021 the second-costliest natural-peril year in Swedish insurance statistics. This time, though, it wasn’t wind that cost money. It was the water.
Storms have not become more frequent
Although storms and wildfires often dominate discussions around climate risk, claims data across the Nordic countries doesn’t point to a clear increase in such perils. By contrast, cloudburst-related water losses display both a strong physical link to a warming climate and a sustained increase in insurance claims. As warmer air holds more moisture, short-duration rainfall events are becoming more intense, placing growing strain on urban drainage systems.
The numbers point the same way
Claims trends are broadly consistent across the region. In Norway, insurers have paid around EUR 3.9 billion in weather-related claims over the past decade, with heavy rainfall in built-up areas accounting for a large share of losses. Denmark has reported elevated cloudburst claims since 2023, while in Sweden flooding and cloudbursts have generated more than 70,000 claims worth around EUR 570 million over the past decade. Together, the data point to a sustained rise in water-related losses rather than isolated catastrophe years.
Why cloudbursts hit buildings so hard
The problem is that much infrastructure is underground. Large parts of the urban drainage networks were laid in the 1950s to 1970s, often for considerably lower rainfall volumes, and in older districts stormwater and sewage still share the same pipe. When such combined systems are overloaded, water is forced back up through the floor drains in the basement. That is precisely the loss type dominating the statistics in both Sweden and Norway: of Swedish flood claims in 2024, more than 60 per cent arose through sewer backup, according to Insurance Sweden.
The volumes involved are easy to underestimate. Events such as the Copenhagen cloudburst of 2011 demonstrated how quickly drainage systems can be overwhelmed when rainfall exceeds design capacity, resulting in widespread basement flooding and major insured losses.
Engineers describe such rainfall in terms of return periods. A 10-year rain is one with a 10 percent probability of occurring in any given year; a 100-year rain has a 1 per cent probability. New drainage networks in Sweden are now designed to cope with return periods of 10 to 30 years depending on building density, with anything heavier to be conveyed away at surface level. Copenhagen 2011 and Gävle 2021 were both far beyond the 100-year level.
The pipes have not deteriorated. They were built for a climate that no longer exists. As cloudbursts intensify, the entire rainfall distribution shifts, so that a rain event that was a 50-year rain when the pipes were laid may today correspond to a 20-year rain. The network still handles exactly the rain it was designed for; the problem is that this rain now arrives more often. By way of example, new systems in Sweden are designed with a climate factor of 1.25 – that is, for 25 per cent more rain than the historical record shows.
Four countries, four ways of carrying the risk
The four Nordic countries insure natural-peril risks differently, ranging from Norway’s compulsory pooling system to the voluntary market-based models used in Sweden and Finland. Despite these differences, insurance penetration is generally high, allowing claims data to provide a reliable indication of how climate-related property losses are evolving across the region.
Insurable, for now
The challenge is no longer confined to an occasional extreme event. A steady increase in recurring water losses is beginning to affect insurance affordability in exposed locations. Industry bodies in several Nordic countries have warned that repeatedly flooded properties are becoming harder to insure on sustainable terms.
Copenhagen’s response following the 2011 cloudburst offers one model. Large-scale investment in stormwater management, combined with property-level resilience measures, has reduced future exposure. Similar initiatives are under way elsewhere in the region, although progress varies.
For insurers, property owners and public authorities, the issue is ultimately one of maintaining insurability. The Nordic countries continue to enjoy some of the world’s strongest natural-peril protection, but preserving that position will depend less on the next major storm than on how effectively urban areas adapt to increasingly intense rainfall.
In brief: what the water costs
- Sweden: 70,000 cloudburst and flood claims for around EUR 570 million, 2015–2024. The record year 2021 (Gävle) cost around EUR 245 million in natural-peril claims in total. (Insurance Sweden)
- Norway: around EUR 3.9 billion in weather-and natural-peril claims over ten years, half of it from heavy rainfall in built-up areas. Stormwater claims up 70 per cent since 2015. (Finance Norway)
- Denmark: 23,000 cloudburst claims in 2023, the most since 2011. Still 12,000 claims in 2025. (Insurance & Pension Denmark)
- Policy definitions of a cloudburst: at least 1 mm/minute or 50 mm/24 hour in Sweden; 40 mm/24 hour in Denmark; 30 mm/hour or 70 mm/24 hour in Finland.
- Currencies: Sweden (SEK), Norway (NOK) and Denmark (DKK) have their own currencies; Finland uses the euro. All amounts in this article are converted to euro.
