sanCheck uses real observation and forecast data from the Korea Meteorological Administration (KMA) and AirKorea to produce an outdoor-activity score that tells you at a glance whether it's a good time to head outside. We explain exactly how that score is built — so that when you see "Caution," you can understand what pulled it down and use that in your own judgment.
The score starts at 0 (best). Each weather indicator is then checked, and the more unfavorable a condition is for being outdoors, the more points it subtracts (a penalty). The penalties from all indicators are added up, and the final total maps to one of the four tiers below. In other words, if nothing warrants a deduction, the score stays at 0 = Optimal; the more bad conditions stack up, the lower it goes.
| Tier | Score range | Meaning |
|---|---|---|
| ● Optimal | 0 | Pleasant, with nothing to deduct |
| ● Fine | -1 to -2 | Minor discomfort, but fine for activity |
| ● Caution | -3 to -5 | Needs preparation or may hamper activity |
| ● Avoid | -6 or lower | Best to hold off on outdoor activity |
Any indicator with no data available (for example, when a station outage leaves the fine-dust value missing) is excluded from the penalty so it doesn't distort the score.
The default rule set factors in five indicators: feels-like temperature, precipitation, wind, UV, and air quality. For each one, only the single worst matching band applies.
Both heat and cold subtract more as they reach extremes.
| Condition | Penalty | Condition | Penalty |
|---|---|---|---|
| 25°C or above | -1 | below 5°C | -1 |
| 31°C or above | -2 | below 0°C | -2 |
| 33°C or above | -3 | below -5°C | -3 |
| 35°C or above | -5 | below -12°C | -5 |
| 38°C or above | -6 | below -15°C | -6 |
If it is currently raining or snowing, -6 points are deducted. Precipitation is the single biggest obstacle to outdoor activity, so on its own it can push the rating to "Avoid."
Wind speed is graded on the international Beaufort scale.
| Beaufort band | Approx. wind speed | Penalty |
|---|---|---|
| Gentle / moderate breeze | 3.4–7.9 m/s | -1 |
| Fresh / strong breeze | 8.0–13.8 m/s | -2 |
| Near gale / gale | 13.9–20.7 m/s | -4 |
| Strong gale or above | 20.8 m/s or above | -6 |
| UV level | Penalty |
|---|---|
| High | -2 |
| Very high | -4 |
| Extreme | -6 |
Of the six air pollutants (fine dust, ultrafine dust, ozone and others), the worst grade becomes the overall air-quality grade used for the penalty. You can change the fine-dust grading standard in settings (compare the standards).
| Air-quality grade | Penalty |
|---|---|
| Bad | -1 |
| Very bad | -3 |
| Hazardous | -6 |
The tables above are sanCheck's default rules. If you feel the cold unusually strongly, or are especially sensitive to fine dust, you can build your own rules under Settings → Weather indicators. Combine the indicators, thresholds, and penalties you want; a rule you create can be shared with others via a share code or imported onto another device. See the usage guide for details.