It's 16°C and the sun is out. Sounds fine for shorts. But there's a steady wind at 35 km/h, and the moment you step outside you feel cheated. Wind is one of the two biggest factors in how warm or cold it actually feels, which is why KorteBroekAan.nl treats it as a first-class input rather than a footnote.
What wind actually does to your body temperature
Your body warms a thin layer of air right against your skin. In still conditions that layer stays put and acts as insulation. Wind strips it away. The faster the wind, the faster your skin loses heat to the surrounding air. This is windchill, and the effect is larger than most people expect.
How much difference does wind make?
At 10°C with no wind, you feel 10°C. At the same temperature with a wind of 30 km/h, the feels-like temperature drops to around 5°C. At 50 km/h you're looking at roughly 2°C.
| Temperature | Wind speed | Feels-like temperature |
|---|---|---|
| 10°C | 0 km/h | ~10°C |
| 10°C | 20 km/h | ~7°C |
| 10°C | 40 km/h | ~3°C |
| 15°C | 0 km/h | ~15°C |
| 15°C | 35 km/h | ~10°C |
| 20°C | 50 km/h | ~15°C |
Below about 15 km/h most people barely notice. Around 25-30 km/h it starts to register. Above 40 km/h it's impossible to ignore. The one exception: on a genuinely hot day (28°C and above), wind feels welcome rather than punishing.
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How KorteBroekAan.nl handles wind
The clothing advice is based on feels-like temperature calculated using the Steadman formula, which incorporates wind speed directly. You can also adjust the Weakling to Legend sensitivity slider, which shifts the temperature threshold at which shorts get recommended. If you run cold, you're a Weakling (no shame in it). If you're still in a t-shirt in October, you're a Legend.
The practical takeaway: wind is not a detail. A moderate to strong wind can push the feels-like temperature 5 to 10 degrees below what the thermometer says. Two days with identical temperatures can feel entirely different depending on whether you're standing in a sheltered courtyard or on an exposed street corner.
Want to understand more about what goes into the feels-like calculation? The other articles in the Weather Explained section cover humidity, cloud cover, rain, and why the thermometer reading alone tells you surprisingly little.
Further reading
Related articles in the Weather Explained section: