Confused about the UV Index?

First published June 2017; updated May 2020

What is solar ultraviolet radiation?

Ultraviolet radiation (UV) is a component of sunlight. The two types of UV that we need to be concerned about are UVA and UVB.

What is the UV index?

The UV index is a scale that was developed by the World Health Organisation which measures the UV level at the surface of the Earth, and gives an indication of the potential for skin damage. It is calculated in a way that indicates the risk of developing sunburn, which is mainly caused by UVB.

Overexposure to UV can cause sunburn, skin and eye damage (including cataracts), and skin cancer. The UV index ranges from zero upwards – the higher the number, the greater the risk. When the UV index is 3 or above, protection is required.

UV levels are influenced by many factors, including: your location (latitude and altitude), time of day, time of year, cloud cover and reflection.

UV cannot be seen or felt (infrared radiation causes heat, not UV) so you need to defend yourself against overexposure.

Know the UV index

In Ireland, make sun protection part of your daily routine particularly from April-September, when the UV index is usually 3 or above, even when it is cloudy. Stay safe by limiting time in the midday sun when UV is strongest, typically between the hours of 11:00am-3:00pm.

The UV index for Ireland is included in Met Éireann’s weather forecasts from May to September but please be aware, that this can only be an average for any one day over the whole country.

Remember the 5 ‘Ss’ of sun safety: Slip, Slop, Slap, Seek, Slide

  • Slip on clothing: Cover skin as much as possible e.g. wear long sleeves, collared t-shirts, clothes made from close-woven material that does not allow sunlight through.
  • Slop on broad-spectrum (UVA/UVB) sunscreen with a sun protection factor (SPF) of at least 30+ for adults and 50+ for children, with high UVA protection, and water resistant. Reapply regularly.
  • Slap on a hat with a wide brim: Protect your face, ears and neck.
  • Seek shade: Sit in cover of trees to avoid direct sunlight and use a sunshade on your buggy or pram. Keep babies and children out of direct sunlight.
  • Slide on sunglasses with UV protection: Guard your eyes from harm.

Next article: Seasonal UV Changes and Protecting Our Skin


We want everyone in Ireland to learn to Protect & Inspect their skin! Read our short guide, written with hospital-based dermatologists, about protecting and checking your skin.   

Click for more about Protect & Inspect!

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