24°C and you feel sticky and overheated. 12°C and the cold seems to get right into you. In both cases, humidity is doing a lot of the work, and in both cases the thermometer reading alone doesn't explain it.
The mechanism on hot days
Your body cools itself by sweating. Sweat evaporates, and evaporation carries heat away from your skin. When the air is already saturated with moisture, that evaporation slows down or stops. Sweat sits on your skin instead of disappearing. You feel hotter, more uncomfortable, and your body has to work harder to regulate its temperature.
On a low-humidity day the reverse applies: sweat evaporates fast, cooling you more efficiently than the air temperature alone would suggest.
| Temperature | Relative humidity | Feels-like temperature |
|---|---|---|
| 25°C | 30% | ~23°C |
| 25°C | 60% | ~26°C |
| 25°C | 85% | ~31°C |
| 30°C | 50% | ~31°C |
| 30°C | 80% | ~38°C |
The difference between 25°C at 30% humidity and 25°C at 85% humidity is eight degrees of perceived temperature. That's not a subtle effect.
The cold side
High humidity in cold weather makes it feel more penetrating. Moist air conducts heat away from your body more readily than dry air, and damp clothing loses its insulating properties faster. A cold drizzly day at 10°C feels noticeably different from a cold dry day at the same temperature.
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How KorteBroekAan.nl uses humidity
Relative humidity feeds directly into the feels-like temperature calculation on the site. You don't need to look it up separately; it's already baked into the number the clothing advice is based on.
This matters more in some climates than others, but for anyone who has experienced a humid summer day or a damp autumn morning, the effect is familiar enough that ignoring it in a clothing recommendation would make the advice genuinely worse.
Humidity is one of several factors the site combines to get a more realistic temperature reading. The other articles in the Weather Explained section cover wind, sunshine, cloud cover, and the rest.
Further reading
Related articles in the Weather Explained section: