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UV Index

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The ozone layer shields the Earth from harmful UV radiation. Ozone depletion, weather, and the seasons cause different amounts of UV radiation to reach the Earth. The UV Index tells you how much. It predicts the next day's UV levels on a 0-11+ scale that helps you decide what to do to be safe in the sun. You can find out what the UV Index forecast is where you live by visiting the UV Index page and entering your zip code.

What follows is a description of each UV Index level, and tips to help you avoid harmful exposure to UV radiation.

The UV Index scale

UV Index Scale

11+: Extreme

A UV Index reading of 11 or higher means extreme risk of harm from unprotected sun exposure. Try to avoid sun exposure during midday hours, from 10 a.m. to 4 p.m. Apply sunscreen with an SPF of at least 15 liberally every 2 hours.

  • Take all precautions. Unprotected skin can burn in minutes. Beachgoers should know that white sand and other bright surfaces reflect UV and will increase UV exposure.
  • Try to avoid sun exposure between 10 a.m. and 4 p.m.
  • Seek shade, cover up, wear a hat and sunglasses, and use sunscreen.

Beat the Heat

It is possible to go outside when the UV Index is 11 or higher. Make sure you always seek shade, wear a hat, cover up, wear 99-100% UV-blocking sunglasses, and use sunscreen. Or you can opt to stay indoors and take the opportunity to relax with a good book rather than risk dangerous levels of sun exposure.

8 - 10: Very High

A UV Index reading of 8 to 10 means very high risk of harm from unprotected sun exposure. Minimize sun exposure during midday hours, from 10 a.m. to 4 p.m. Protect yourself by liberally applying a sunscreen with an SPF of at least 15. Wear protective clothing and sunglasses to protect the eyes.

  • Take extra precautions. Unprotected skin will be damaged and can burn quickly.
  • Minimize sun exposure between 10 a.m. and 4 p.m. Otherwise, seek shade, cover up, wear a hat and sunglasses, and use sunscreen.

Stay in the Game

Be careful during routine outdoor activities such as gardening or playing sports. Remember that UV exposure is especially strong if you are working or playing between the peak hours of 10 a.m. and 4 p.m. Don't forget that spectators, as well as participants, need to wear sunscreen and eye protection to avoid too much sun.

6 - 7: High

A UV Index reading of 6 to 7 means high risk of harm from unprotected sun exposure. Apply a sunscreen with a SPF of at least 15. Wear a wide-brim hat and sunglasses to protect your eyes.

  • Protection against sunburn is needed.
  • Reduce time in the sun between 10 a.m. and 4 p.m.
  • Cover up, wear a hat and sunglasses, and use sunscreen.

Made in the Shades

Wearing sunglasses protects the lids of your eyes as well as the lens.

3 - 5: Moderate

A UV Index reading of 3 to 5 means moderate risk of harm from unprotected sun exposure.

  • Take precautions, such as covering up, if you will be outside.
  • Stay in shade near midday when the sun is strongest.

Me and My Shadow

An easy way to tell how much UV exposure you are getting is to look for your shadow:

  • If your shadow is taller than you are (in the early morning and late afternoon), your UV exposure is likely to be low.
  • If your shadow is shorter than you are (around midday), you are being exposed to high levels of UV radiation. Seek shade and protect your skin and eyes.

2 or less: Low

A UV Index reading of 2 or less means low danger from the sun's UV rays for the average person:

  • Wear sunglasses on bright days. In winter, reflection off snow can nearly double UV strength.
  • If you burn easily, cover up and use sunscreen.

Look Out Below

Snow and water can reflect the sun's rays. Skiers and swimmers should take special care. Wear sunglasses or goggles, and apply sunscreen with an SPF of at least 15. Remember to protect areas that could be exposed to UV rays by the sun's reflection, including under the chin and nose.