Every city shows the same standard readings — temperature, feels-like, air quality, rain, wind, UV, humidity. The headline on each card is the worst thing in the sky over the next 24 hours, whether that is smoke, heat, a storm, hail, snow, wind or an earthquake. Star a city to keep it at the top.
Every hazard is scored on one shared scale, 0 nothing · 1 notable · 2 watch · 3 warning · 4 severe, from measurements in the next 24 hours of each city's own local time. The highest score is the headline; ties go to the hazard that kills faster. The rules are in hazards.js and tested.
| Hazard | Measured | 1 | 2 | 3 | 4 |
|---|---|---|---|---|---|
| Air | US AQI now | ≥101 | ≥151 | ≥201 | ≥301 |
| Heat | peak feels-like °C | ≥34 | ≥38 | ≥42 | ≥46 |
| Cold | low feels-like °C | ≤0 | ≤−10 | ≤−20 | ≤−30 |
| Rain | mm in 24 h, when ≥60 % likely | ≥5 | ≥20 | ≥50 | ≥100 |
| Thunderstorms · Hail | WMO code 95 · 96/99 | storm | hail | ||
| Snow · Blizzard | cm in 24 h · plus gusts ≥60 km/h | ≥1 | ≥10 | ≥25 | blizzard |
| Wind | peak gust km/h | ≥60 | ≥80 | ≥100 | ≥120 |
| UV | daily peak index | ≥8 | ≥11 | ||
| Fog | WMO 45/48 in the next 6 h | fog | |||
| Earthquake | magnitude within 300 km, past 24 h (+1 if within 100 km) | ≥4.0 | ≥5.0 | ≥6.0 | ≥7.0 |