The thermometer reads 18°C, yet you still feel cold. Or the opposite: barely 22°C but it feels thick and uncomfortable. That's the feels-like temperature at work, and it's why KorteBroekAan.nl uses that number rather than raw air temperature.
What is feels-like temperature?
Feels-like temperature (also called apparent temperature) is how warm or cold it actually feels to a person standing outside. Air temperature alone doesn't capture that. Two things matter a lot:
Wind pulls heat away from your skin faster. The stronger the wind, the colder you feel — this is windchill. Humidity works the other way: when the air is saturated, sweat evaporates slowly, so your body can't cool itself properly and you feel hotter than the thermometer suggests.
How is it calculated?
The most widely used method is the Steadman formula, applied by meteorologists worldwide. It takes three inputs: air temperature (°C), wind speed (km/h) at 10 metres height, and relative humidity (%).
At low temperatures, windchill dominates. At high temperatures, humidity takes over — this is the heat index effect.
Windchill example
10°C with a 30 km/h wind feels like about 5°C. Your skin loses heat roughly five times faster than in still air.
Heat index example
30°C with 80% humidity feels like about 38°C. That's the range where strenuous outdoor activity gets genuinely risky.
Why does KorteBroekAan.nl use feels-like temperature?
Because "can I wear shorts?" doesn't depend on what the thermometer says. A 20°C day with strong wind and high humidity can easily feel like 14°C. Shorts are a bad idea in that weather, regardless of the number on the screen.
The threshold is based on feels-like temperature, not measured temperature. With the default sensitivity setting:
- Feels-like above 15°C and rain chance below 90% → shorts on ✓
- Feels-like 15°C or lower, or rain chance 90% or more → shorts off ✗
In settings you can pick a different mode: Weakling (never shorts), Daring (above 10°C and rain chance below 95%) or Legend (always shorts).
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What does this look like in practice?
| Air temperature | Wind | Humidity | Feels-like | Advice |
|---|---|---|---|---|
| 20°C | 5 km/h | 50% | ~19°C | Shorts ✓ |
| 20°C | 40 km/h | 60% | ~15°C | Borderline |
| 18°C | 25 km/h | 70% | ~13°C | Long trousers ✓ |
| 25°C | 10 km/h | 85% | ~28°C | Shorts ✓ |
Conclusion
Raw air temperature is a poor proxy for how you actually feel outside. Wind and humidity shift the equation enough that ignoring them gives bad clothing advice. That's the whole point of using feels-like temperature.
More weather factors that affect the shorts decision are covered in the other Weather Explained articles.
Further reading
Related articles in the Weather Explained section:
Read next
Why cloud cover matters for clothing advice
The same thermometer reading feels completely different under a clear sky versus a grey one. Cloud cover changes how much solar radiation actually reaches you.
Why humidity matters for clothing advice
Humidity works in both directions: it makes hot days feel suffocating and cold days feel more biting. Here's what's actually happening and why KorteBroekAan.nl includes it.
Why rain probability matters for clothing advice
A 60% chance of rain doesn't mean it will rain 60% of the time. Here's what rain probability actually tells you and when it should change what you wear.
Why rainfall amount matters for clothing advice
The difference between drizzle and a downpour isn't just about getting wet. Rainfall intensity in mm per hour changes how quickly clothing fails as insulation.
Feels-like vs air temperature: what's the difference?
Weather apps show air temperature, but your body responds to feels-like temperature. The gap between the two can be 10 degrees or more. Here's what drives that difference.