When there is still sunlight at 5pm, and the temperature is just as hot as it is at 1pm, why is the UV index significantly lower in the evening?

Question

When there is still sunlight at 5pm, and the temperature is just as hot as it is at 1pm, why is the UV index significantly lower in the evening?

In: Planetary Science

Answer 1

In addition to what has been mentioned: The atmosphere absorbs UV pretty well, but doesn’t absorb visible light much. At noon you get almost all the sunlight and maybe 10% of the UV compared to space. At 5 pm the light crosses twice as much air, you still get almost all the visible light but only 10% of 10% = 1% of the UV. The numbers depend on the location and the day, but the general concept is the same everywhere. Temperature and visible light are not an indication for the UV index.