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Understanding UV radiation

The sun sends out different types of radiation.

There's visible light we see as sunlight, infrared radiation we feel as heat, and ultraviolet (UV) radiation we can't see or feel. So even when the temperature is lower and/or skies are cloudy, skin-damaging UV radiation can still be high.

There are two types of UV radiation that affect our risk of developing skin cancer:

  • UVA can cause sunburn, DNA (cell) damage in the skin and skin cancer.
  • UVB causes skin damage and skin cancer – luckily ozone in the atmosphere stops most UVB from reaching the earth's surface.

Factors affecting levels of UV radiation

Levels of UV radiation change throughout the day, month and year across New Zealand.

The total amount of UV radiation present is affected by:

  • proximity to the equator
  • time of day
  • time of year
  • cloud cover
  • altitude
  • scattering
  • reflection.

Visit NIWA’s website to discover more about UV radiation and ozone or to find today’s UV index reading. The Australian Radiation Protection and Nuclear Safety Agency also has useful UV information.

Know the sun protection times for your region

Sun Protection Alert

Developed by the Health Promotion Agency in association with MetService and NIWA, the Sun Protection Alert is available during daylight saving months. It provides the recommended times to be SunSmart each day for specific areas of New Zealand.

This is based on the UV index (UVI), where a UVI of greater than 10 is extreme and a UVI of less than 3 is low. 

You can add the Sun Protection Alert to your workplace’s website and intranet. It will display the UV reading for your selected region so your people know when they should be SunSmart.

The alert is specific to regions across the country and alert times can change in five-minute increments from one day to the next.

Available during daylight saving months, the Sun Protection Alert can be accessed through the Metservice website homepage and the SunSmart website. It may also be printed in your local daily newspaper.

uv2Day smartphone app

Another useful tool is the uv2Day app, developed in consultation with NIWA.

Using NIWA's UV forecasts, the app shows the current UV index level, its peak value, and its progression throughout the day. It means people - especially those with melanoma or sensitive skin - can make up-to-the-minute decisions about their time outdoors.

Particularly if your people spend a lot of time in the sun, consider encouraging them to download this free app.

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