Two days in a row, both sitting at 14°C. On the cloudy one you reach for a jacket without thinking. On the sunny one a light shirt feels fine, maybe even warm by midday. The thermometer hasn't changed. What has changed is whether the sun is actually reaching you.
Why sunlight adds warmth the thermometer doesn't capture
The sun emits infrared radiation that passes straight through the air and gets absorbed directly by your skin. Air temperature barely shifts as a result, but your body picks up the energy immediately. On a still, sunny day that can add 3 to 8 degrees of perceived warmth, and in summer the effect can reach 10 degrees.
How much you gain depends on a few things. The angle of the sun matters a lot: high in summer, low in winter. Clouds block direct radiation almost entirely when the sky is fully overcast. Wind can strip away the warmth the sun just added, which is why a breezy sunny day and a calm cloudy day can end up feeling remarkably similar even though they look completely different.
Can you wear shorts today?
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How KorteBroekAan.nl accounts for sunshine
The site factors cloud cover into its feels-like temperature calculation. On a clear day the threshold for recommending shorts gets reached at a lower air temperature than on a grey one. A 14°C sunny forecast might tip the advice toward lighter clothing; the same 14°C under thick cloud probably won't.
The practical gap is real. A sunny 14°C day can feel like 19°C. The same 14°C overcast with a bit of wind can feel closer to 10°C or 11°C. If you've ever been surprised by how warm a spring morning felt despite the forecast looking modest, or how grey and chilly a day seemed despite the number on the app, this is why.
Sunshine is only part of the picture. The other articles in the Weather Explained section cover how wind, cloud cover, humidity, and rainfall all feed into what you'll actually feel outside.
Further reading
Related articles in the Weather Explained section: