Fact: UV Index

Today is a sunny day in Pennsylvania. However, we cannot judge the intensity of the sun’s rays by cloud cover alone.

The angle of the sun (determined by time of year and time of day), the altitude at which we stand, the reflective qualities of what we are standing next to (snow, water, etc.) and the thickness of the ozone layer over our tiny spec on the earth all affect the strength of the UVA and UVB rays that reach us.


Expert mathematical calculations went into the Experimental Ultraviolet Index when it was announced as part of the Federal government’s Sunwise program in 1994. Today, the UV Index is forecast daily for 58 major cities across America, using those calculations.

This tool was created so that I could take proactive measures to protect my skin and eyes. Thus, I will begin to include Philadelphia’s forecast in the heading of this daily blog.

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