A weather forecast is full of indicators — probability of precipitation, sky condition, feels-like temperature, UV index, fine-dust grades — that become far more useful once you know exactly what they mean. Here's what the values in sanCheck actually represent, and how to read a Korea Meteorological Administration (KMA) forecast, one indicator at a time.
This is the chance that rain or snow will fall at a given time and place, shown as a percentage. Contrary to a common misreading, a 70% POP does not mean "rain at 70% intensity" or "rain over 70% of the area" — it means there is a 70% chance that it rains at all. A high probability also doesn't guarantee heavy rain. As a rule of thumb, 30% or below is usually fine without an umbrella, while 60% or above is worth carrying one.
KMA's short-term forecast divides the sky into three states — Clear · Mostly cloudy · Overcast — based on how much cloud covers the sky. "Mostly cloudy" means plenty of cloud but no rain.
When rain or snow is expected, a precipitation type is shown as well: none · rain · rain/snow (sleet) · snow · shower. In winter, the same precipitation falls as rain or snow depending on temperature.
Air temperature is what the thermometer reads, while feels-like temperature factors in wind and humidity to estimate what a person actually feels. In winter, stronger wind makes it feel colder than the reading (wind strips away body heat); in summer, higher humidity keeps sweat from evaporating, so it feels hotter. sanCheck's score is based on this feels-like temperature, not the raw air temperature.
The UV index expresses the effect of ultraviolet radiation on skin on a scale from 0 to 11+. The higher it is, the greater the risk of skin damage from even brief exposure.
| Index | Level | What to do |
|---|---|---|
| 0–2 | Low | No special action needed |
| 3–5 | Moderate | Hat and sunglasses advised |
| 6–7 | High | Seek shade, use sunscreen |
| 8–10 | Very high | Avoid midday sun outdoors |
| 11+ | Extreme | Stay indoors if possible |
The same dust concentration can read as "Moderate" under one standard and "Bad" under another. In Settings → Fine-dust standard, sanCheck lets you choose one of three standards. All units are µg/m³ (micrograms per cubic meter).
| Standard | Good | Moderate | Bad | Very bad |
|---|---|---|---|---|
| Korea (Ministry of Env.) | ~30 | ~80 | ~150 | 150+ |
| WHO 2021 | ~20 | ~45 | ~70 | 70+ |
| WHO extended (default) | ~20 | ~45 | ~70 | ~150* |
| Standard | Good | Moderate | Bad | Very bad |
|---|---|---|---|---|
| Korea (Ministry of Env.) | ~15 | ~35 | ~75 | 75+ |
| WHO 2021 | ~10 | ~25 | ~37.5 | 37.5+ |
| WHO extended (default) | ~10 | ~25 | ~37.5 | ~75* |
* The WHO-extended standard follows the WHO 2021 guideline values but adds one more tier — "Hazardous" — above "Very bad" (PM10 over 150, PM2.5 over 75). It is the default because it reflects the WHO's strict guidance while still singling out the genuinely dangerous high-concentration days.
When hazardous weather is expected, KMA issues an advisory, and a more serious warning for severe cases. They cover heavy rain, heavy snow, heat, cold, strong wind, dry conditions, and yellow dust, among others; a warning denotes a level more dangerous than an advisory. When an alert is in effect for a location you've saved, sanCheck shows it right on the screen.