Severe storms caused over $100 billion in insured losses globally in 2024, making it the costliest storm year on record according to Munich Re. From tropical cyclones to severe thunderstorms, storm risk is intensifying as a warmer atmosphere fuels more energetic weather systems.
Storm risk measures the frequency and intensity of severe wind events at a given location. As one of the 12 physical risk hazards in climate risk assessment, storm risk captures the number of days per year when wind speeds exceed extreme thresholds, indicating the potential for structural damage, power outages, and disruption to transportation and supply chains.
What Is Storm Risk?
Storm risk is the probability and potential severity of extreme wind events affecting a location. Severe storms generate winds that exceed the structural design capacity of buildings, topple power lines, uproot trees, and create hazardous conditions for transportation and outdoor operations.
Storm risk is location-dependent. Coastal regions face tropical cyclone exposure. Continental interiors experience severe thunderstorms and tornadoes. Mid-to-high latitudes encounter extratropical storms and blizzards. A location’s storm risk profile depends on its geographic position, local topography, and historical storm track patterns.
In climate risk screening, storm risk is measured as the number of severe storm days per year when surface wind speeds exceed the 95th percentile of historical observations. Locations that regularly experience extreme wind events face higher baseline storm risk, while climate change projections indicate whether this frequency is likely to increase.
Types of Severe Storms
Four categories of severe storms represent different storm risk profiles, each driven by distinct atmospheric mechanisms:
Tropical cyclones. Known as hurricanes in the Atlantic and typhoons in the Pacific, tropical cyclones are the most destructive storm type globally. Sustained winds exceeding 119 km/h (Category 1 hurricane), combined with storm surge and extreme rainfall, cause catastrophic damage to coastal communities. Tropical cyclone storm risk is concentrated in Atlantic, Pacific, and Indian Ocean basin coastlines.
Tornadoes. Rotating columns of air that descend from thunderstorm clouds, tornadoes produce the most extreme winds observed on Earth, with the strongest exceeding 400 km/h. Tornado storm risk is highest in the central United States, Bangladesh, and parts of Europe and South America.
Severe thunderstorms. Large convective systems that produce damaging winds exceeding 93 km/h, large hail, and intense rainfall. Thunderstorm storm risk is most common in continental interiors where warm, moist air masses collide with cooler air, creating atmospheric instability.
Extratropical and winter storms. Large-scale low-pressure systems that bring blizzards, ice storms, and sustained strong winds to mid-to-high latitude regions. Extratropical storm risk affects northern Europe, the northeastern United States, and similar maritime climates.
How Climate Change Affects Storm Risk
Climate change alters storm risk through multiple pathways, though the relationship varies by storm type:
Tropical cyclone intensification. Warmer sea surface temperatures provide more energy to tropical cyclones, increasing peak wind speeds and rainfall intensity. The IPCC Sixth Assessment Report projects that the proportion of Category 4-5 hurricanes will increase, even if total cyclone frequency remains stable or slightly decreases.
Increased atmospheric instability. A warmer atmosphere holds more moisture and generates greater convective energy, fueling more intense thunderstorms. Regions that already experience severe convective storm risk may see more frequent damaging wind events and larger hail.
Shifting storm tracks. Changes in jet stream patterns and atmospheric circulation are altering where storms travel. Mid-latitude storm tracks are shifting poleward, potentially reducing storm risk at some locations while increasing it at others. Extratropical storms may become less frequent overall but more intense individually.
Compound hazards. Storms interact with other climate hazards. Tropical cyclones produce extreme rainfall that causes flooding and landslides. Winter storms combined with freezing temperatures create compound cold stress events. Storm risk assessment benefits from understanding these interactions.
How Is Storm Risk Assessed?
Storm risk assessment uses the surface wind speed variable (sfcWind) from NASA NEX-GDDP-CMIP6 climate projections. The methodology identifies severe storm days based on wind speed exceeding the 95th percentile of baseline observations.
The approach calculates a storm threshold from historical wind speed data, then projects how the number of days exceeding that threshold changes under future climate scenarios:
| Risk Rating | Severe Storm Days/Year | Impact Level |
|---|---|---|
| Low | Less than 5 | Rare extreme wind events |
| Moderate | 5-15 | Seasonal storm exposure |
| High | 15-30 | Frequent damaging winds |
| Severe | 30-50 | Regular structural wind damage risk |
| Extreme | Greater than 50 | Chronic storm exposure |
It is important to note that this methodology captures general severe wind patterns but does not model individual storm types (hurricanes, tornadoes) directly. Wind speed data provides a proxy for overall storm risk exposure rather than hazard-specific forecasts. Platforms like Continuuiti assess storm risk alongside 11 other climate hazards for a complete physical climate risk assessment.
Frequently Asked Questions
What is storm risk?
Storm risk is the probability and severity of extreme wind events at a location, measured as severe storm days per year when wind speeds exceed the 95th percentile of historical data. Storm risk captures exposure to tropical cyclones, tornadoes, thunderstorms, and extratropical storms.
What are the types of severe storms?
The four main types are tropical cyclones (hurricanes/typhoons), tornadoes, severe thunderstorms, and extratropical/winter storms. Each has distinct atmospheric drivers and geographic distribution patterns.
Does climate change increase storm risk?
Climate change intensifies tropical cyclones through warmer sea surfaces, fuels stronger thunderstorms with increased atmospheric moisture, and shifts storm tracks. The proportion of the most intense hurricanes is projected to increase under warming scenarios.
How is storm risk measured in climate assessment?
Storm risk uses NASA NEX-GDDP-CMIP6 surface wind speed data. Severe storm days are counted when wind exceeds the 95th percentile baseline. Risk is rated from Low (fewer than 5 days/year) to Extreme (more than 50 days/year) under multiple emissions scenarios.
Storm risk remains one of the most impactful physical hazards, with insured losses growing as climate change intensifies storm systems and expanding development increases exposure. Screening storm risk alongside other hazards like flooding and rainfall intensity reveals where compound storm damage is most likely to occur.
