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When the UV index is presented on a daily basis, it represents UV intensity around the sun's highest point in the day, called solar noon, halfway between sunrise and sunset. This typically occurs between 11:30 and 12:30, or between 12:30 and 13:30 in areas where daylight saving time is being observed.
The time of day. In most locations, the sun's rays are strongest between approximately 10 am and 4 pm daylight saving time. [19] Cloud cover. Clouds partially block UV, but even on an overcast day, a significant percentage of the sun's damaging UV radiation can pass through clouds. [20] [21]
Highest ultraviolet index measured: On 29 December 2003, a UV index of 43.3 was detected at Chile/Bolivia's Licancabur volcano, at 19,423 feet (5,920 m) altitude. A light-skinned individual in such conditions may experience moderate sunburn in as little as 4 minutes.
The latest TikTok tanning trend involves monitoring the UV index and timing sunbathing sessions to when it's high, but experts say that exposing yourself to strong ultraviolet rays is a bad idea.
Sunburn effect (as measured by the UV index) is the product of the sunlight spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths. Sunburn production per milliwatt of radiation intensity is increased by nearly a factor of 100 between the near UVB wavelengths of 315–295 nm.
[17] [18] [19] UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D. [20] Time of day, time of year, geographic latitude, ground altitude, cloud cover, smog, skin melanin content, and sunscreen are among the factors that greatly affect UV intensity and vitamin D synthesis, [19 ...
With the exception of Madrid, [9] Lisbon [10] and Athens, [11] Rome has the highest UV index between European capitals (only in the continent) and values close to that of Chicago at 41.9 °N as ultraviolet radiation is less interfered with by other geographic variables, but with a moderate annual average with index equal to 5, which allows ...
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