Extreme Weather Probability Calculator

The calculator combines your climate region, average temperature, annual rainfall, warming trend, and proximity to water to estimate the annual probability of extreme weather events. It uses weighted scoring models based on established climatological relationships — for example, each degree of warming roughly doubles the frequency of heat waves, while rainfall changes and elevation drive flood risk.

The warming trend is how much hotter your local area is compared to pre-industrial (circa 1850–1900) baseline temperatures. The global average is approximately 1.2°C as of 2024. Higher warming trends strongly amplify the probability of heat waves and intensify storm activity due to increased atmospheric energy.

Being near rivers, coasts, or flood plains raises flood probability significantly — coastal areas face both riverine flooding and storm surge risk. Living on a flood plain can triple or quadruple baseline flood probability. Inland and elevated locations have much lower flood risk but may still face severe storms and heat waves.

Urban areas absorb and retain heat more than rural landscapes, effectively adding an extra 0.5°C to 2°C of local warming on top of the regional climate trend. This increases the likelihood and severity of heat waves in cities, and can also intensify local storm activity due to greater surface heating.

No — the calculator outputs probabilities, not certainties. A 70% heat wave probability means that under current climate conditions, heat waves are very likely in your region over a given year, but individual events depend on many unpredictable factors. Think of this as a risk assessment tool, not a precise forecast.

Climate change is shifting the statistical baselines that forecasting models are built on. Events that were once considered '100-year' storms are now occurring every 10–20 years in many regions. Increased atmospheric moisture and energy create more volatile conditions, making precise timing harder while making the overall probability of extremes higher.

The Risk Score is a composite index out of 100 that combines heat wave, flood, storm, and drought probabilities weighted by your regional climate profile. A score above 60 indicates high overall risk; above 80 suggests very high risk requiring proactive climate adaptation planning. The score is best used for comparison — for example, comparing the risk before and after a warming trend increase.

Increased rainfall raises flood probability but reduces drought risk, while decreased rainfall does the opposite. However, climate science shows that even wetter regions can face more intense droughts between heavy rainfall events — a phenomenon called 'precipitation whiplash' — so both risks can be elevated at the same time in some climates.