The UV Index is a forecast of the probable intensity of skin damaging ultraviolet radiation reaching the surface during the solar noon hour: 11:30-12:30 Local Standard Time, or 12:30-13:30 Local Daylight Time. The greater the UV Index is the greater the amount of skin damaging UV radiation. How much UV radiation is needed to actually damage one's skin is dependent on several factors. In general, the darker one's skin is — that is, the more melanin one has in his/her skin — the longer (or the more UV radiation) it takes to cause erythema (skin reddening).
The figure above shows a look-up chart where you may cross check your propensity to burn versus the UV Index. For those who always burn and never tan, the times to burn are relatively short compared to those who almost always tan.
The EPA has devised general guidelines as far as what to do to protect oneself from overexposure to UV radiation. These are shown in the table below.
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