What time of the day are UV rays at their strongest?

First published June 2017; updated May 2019

UV radiation in sunlight damages our skin. UV radiation cannot be seen or felt (infrared radiation causes heat, not UV). It can damage skin on cool, cloudy days and hot sunny days.

UV radiation comes directly from the sun and is influenced by many factors including

  • Latitude
  • Time of the day
  • Time of year
  • Altitude
  • Reflection


The Global solar UV index is a scale that was developed by the World Health Organisation which measures the UV radiation level at the surface of the earth and gives indication of the potential for sun damage. The UV index ranges from zero upwards – the higher the UV index the greater the risk.

Whenever the UV index reaches 3 and above, sun protection is required because of skin and eye damage. UV index levels reach their peak in the middle of the day so extra care should be taken between 11am-3pm. The UV index is available on Met Eireann’s website.

Related: Clouds, water, glass: surprising things that solar UV can pass through.

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

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