How accurate is it?
We test our scores against real floods seen from space, official government flood maps and weather stations. Every test is open and repeatable. Last run 2026-11-09.
8,750 points in 19 floods. 79% in or within 200 m of our zone.
Flooded spots 67% vs nearby dry spots 26%.
vs 81 weather stations.
Places rank in nearly the same order as stations (1.0 = same).
River flood vs real floods
Copernicus maps the water from satellites after big floods. We picked random spots that really flooded, and random spots nearby that stayed dry, then scored them.
| Group | Floods | Flooded spots flagged | Flagged or within 200 m | Dry spots flagged | AUC |
|---|---|---|---|---|---|
| All floods | 19 | 67% | 79% | 26% | 0.74 |
| River floods | 18 | 69% | 80% | 29% | 0.74 |
| Flash floods | 3 | 52% | 69% | 4% | 0.81 |
"Dry spots flagged" is not a pure false-alarm rate. One flood rarely fills a whole flood zone, so many flagged dry spots are still at real risk. AUC is the chance a flooded spot scores higher than a dry one (0.5 = coin flip, 1.0 = perfect).
Every flood tested
| Flood | Date | Type | Flagged | Flagged or near | Dry flagged |
|---|---|---|---|---|---|
| Flood in Emilia-Romagna, Italy EMSR659 AOI01 | 2023-05 | riverine | 52% | 65% | 43% |
| Flood in Emilia-Romagna, Italy EMSR659 AOI02 | 2023-05 | riverine | 0% | 75% | 20% |
| Flood in Mozambique EMSR663 AOI01 | 2023-03 | riverine | 70% | 88% | 20% |
| Flood in Slovenia EMSR680 AOI01 | 2023-08 | riverine | 30% | 43% | 3% |
| Flood in Slovenia EMSR680 AOI03 | 2023-08 | riverine | 7% | 15% | 4% |
| Flood in Greece EMSR692 AOI01 | 2023-09 | riverine | 35% | 44% | 12% |
| Flood in Greece EMSR692 AOI02 | 2023-09 | riverine | 89% | 97% | 14% |
| Flood in Libya EMSR696 AOI01 | 2023-09 | flash | 51% | 75% | 2% |
| Flood in Libya EMSR696 AOI02 | 2023-09 | flash | 1% | 15% | 2% |
| Flood in Thessaly and Sterea Ellada regions, Greece EMSR697 AOI01 | 2023-09 | flash | 69% | 88% | 6% |
| Flood in Thessaly and Sterea Ellada regions, Greece EMSR697 AOI04 | 2023-09 | riverine | 2% | 6% | 0% |
| Flood in Rio Grande Do Sul State, Brazil EMSR720 AOI01 | 2024-05 | riverine | 94% | 100% | 29% |
| Flood in Rio Grande Do Sul State, Brazil EMSR720 AOI02 | 2024-05 | riverine | 76% | 93% | 23% |
| Flood in Germany EMSR728 AOI01 | 2024-05 | riverine | 100% | 100% | 4% |
| Flood in Germany EMSR728 AOI03 | 2024-05 | riverine | 95% | 99% | 26% |
| Flood in Borno, Nigeria EMSR753 AOI01 | 2024-09 | riverine | 70% | 96% | 12% |
| Flood in Germany EMSR763 AOI01 | 2024-09 | riverine | 78% | 94% | 70% |
| Flood in Croatia and Slovenia EMSR768 AOI01 | 2024-10 | riverine | 97% | 100% | 44% |
| Flood in Croatia and Slovenia EMSR768 AOI02 | 2024-10 | riverine | 92% | 95% | 12% |
| Flood in Emilia- Romagna, Italy EMSR771 AOI01 | 2024-10 | riverine | 37% | 52% | 15% |
| Flood in Emilia- Romagna, Italy EMSR771 AOI04 | 2024-10 | riverine | 0% | 0% | 0% |
| Flood in Cameroon EMSR772 AOI01 | 2024-10 | riverine | 74% | 83% | 26% |
| Flood in Cameroon EMSR772 AOI02 | 2024-10 | riverine | 100% | 100% | 95% |
| Flood in Valencia Region, Spain EMSR773 AOI01 | 2024-10 | flash | 89% | 96% | 5% |
| Flood in Valencia Region, Spain EMSR773 AOI02 | 2024-10 | riverine | 38% | 85% | 2% |
| Flood in Cameroon EMSR779 AOI01 | 2024-11 | riverine | 71% | 86% | 27% |
| Flood in Cameroon EMSR779 AOI02 | 2024-11 | riverine | 100% | 100% | 96% |
| Flood in Scotland, United Kingdom EMSR783 AOI01 | 2024-12 | riverine | 64% | 70% | 2% |
| Flood in Scotland, United Kingdom EMSR783 AOI03 | 2024-12 | riverine | 95% | 100% | 10% |
| Flood in Pakistan EMSR838 AOI01 | 2025-08 | riverine | 84% | 96% | 58% |
| Flood in Pakistan EMSR838 AOI02 | 2025-08 | riverine | 98% | 100% | 92% |
| Flood in Mozambique and South Africa EMSR857 AOI01 | 2026-01 | riverine | 100% | 100% | 70% |
| Flood in Mozambique and South Africa EMSR857 AOI02 | 2026-01 | riverine | 95% | 97% | 24% |
| Flood in Evros River basin, Greece EMSR868 AOI01 | 2026-02 | riverine | 98% | 99% | 22% |
| Flood in Evros River basin, Greece EMSR868 AOI02 | 2026-02 | riverine | 92% | 95% | 22% |
River flood vs official flood maps
Government flood maps are built with local surveys. We compared random spots in inland river towns. Like ours, both maps ignore flood walls.
| Map | Towns | Points | Official 1% zone we flag | Outside zones we flag | Agreement | AUC |
|---|---|---|---|---|---|---|
| England (Environment Agency) | 10 | 4,000 | 74% | 5% | 90% | 0.85 |
| United States (FEMA) | 10 | 3,000 | 82% | 13% | 86% | 0.88 |
Heat, rain and frost vs weather stations
111 quality-checked stations in 6 regions, 2005-2024. Same years on both sides.
| Measure | Stations | Typical gap | Typical lean | Ranking match |
|---|---|---|---|---|
| Days over 35 C a year | 81 | 2.5 days/yr | -0.8 days/yr (-25%) | 0.83 |
| Hottest day of the year | 81 | 1.6 C | -1.4 C (-3%) | 0.89 |
| Rain per year | 74 | 94.5 mm/yr | +50.0 mm/yr (+11%) | 0.96 |
| Wettest day of the year | 74 | 11.0 mm | -10.5 mm (-24%) | 0.85 |
| Frost nights a year | 68 | 9.6 days/yr | 0.0 days/yr (-2%) | 0.96 |
| Hazard grade (A-E) | Stations | Same grade | Within one grade |
|---|---|---|---|
| Extreme heat | 81 | 62% | 91% |
| Drought | 74 | 69% | 99% |
| Heavy rain | 74 | 42% | 88% |
| Frost and cold | 68 | 74% | 96% |
By region
| Region | Stations | Hottest day gap | Hot days gap | Wettest day lean |
|---|---|---|---|---|
| Africa | 20 | 1.5 C | 15.3 days | 9% |
| Middle East | 20 | 0.9 C | 9.9 days | -25% |
| Europe | 20 | 2.5 C | 0.1 days | -24% |
| South and East Asia | 20 | 1.9 C | 2.2 days | -38% |
| North America | 20 | 1.5 C | 5.0 days | -22% |
| Latin America | 11 | - | - | - |
A station is one spot. Our climate data is an average over about 50 km, so local extremes, mostly rain bursts, read lower.
What this means in practice
Good for
Screening many sites fast. Ranking a portfolio by risk. Finding which sites need a closer look.
Weaker on
Flash floods from local rain (52% flagged). Coastal surge. Rain extremes, which read about 24% low.
Not for
Engineering design, insurance pricing on its own, or life-safety decisions. Use a site survey for those.
Method and data
Points are sampled with a fixed random seed, so anyone can rerun the tests and get the same numbers. Raw results: accuracy.json.
Flood footprints: Copernicus Emergency Management Service (c) European Union. England flood zones: contains Environment Agency information (c) Environment Agency and/or database right, Open Government Licence v3.0. US flood zones: FEMA National Flood Hazard Layer, via Esri Living Atlas. Stations: NOAA NCEI GHCN-Daily. Hazard maps: JRC/GloFAS v2.1 (CC BY 4.0) and NASA POWER.