I was inspired by this question to ask, what causes the "beating down" feeling of the sun to vary day to day? While the linked post explains why the sun feels hotter in the summer than in the winter, what causes more short term variations in the perceived intensity of the sun?

Why does the sun often feel more intense on some days and less intense on others? Why can the sun often feel oppressively hot even when the air is cool, while other times the sun might feel pleasant even when the air is warm?

Also related: Why is the sun brighter in Australia compared to parts of Asia?

  • $\begingroup$ have you read this article ? en.wikipedia.org/wiki/Heat_wave $\endgroup$
    – anna v
    Apr 13 '18 at 3:50
  • $\begingroup$ Yes, I find it only somewhat helpful as the language used is not particularly easy to understand without more knowledge of how pressure systems work. But my question also pertains to short term variations in the perceived intensity of the sun. $\endgroup$
    – Kai
    Apr 13 '18 at 3:58

When you feel "heat" from the Sun, what you're actually feeling is the infrared radiation that the Sun emits. The reason infrared radiation feels hot is because your body is mostly water, and infrared radiation tends to vibrate the bonds of water molecules.

But if there's a lot of water in the air, then the infrared radiation will be absorbed by the water in the air before it hits your body, so the Sun will feel less hot. Therefore, on humid days, you don't feel the Sun "beating down on you" quite as hard as on dry days (even though you may, overall, feel hotter on humid days due to your inability to cool via evaporation of sweat). Day-to-day "hotness" fluctuations of the Sun are most likely due to changes in humidity.

  • $\begingroup$ Thanks, this is a simple and easy to understand answer and makes perfect sense. $\endgroup$
    – Kai
    Apr 13 '18 at 4:44

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