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UV index

Find out the UVI in your area and get your own personal recommendations. Or text your town or city to 2227 to get UVI data for your area sent straight to your mobile phone (find out more about text alerts).

The ultraviolet radiation index (UVI) is a measure of the intensity of ultraviolet (UV) radiation in our environment. The higher the UVI number the more intense the UV radiation. Find out the UVI in your town.

Too much exposure to UV radiation from the sun can be very dangerous. It contributes to over 300 deaths from skin cancer each year.

When the UVI is at 3 or higher we all need to protect ourselves. This happens almost daily from September to March. It can also happen in winter, especially at high altitudes and in snow – so remember to protect yourself when you go skiing or snowboarding.

Throughout a day UV radiation behaves in a predictable way. It is highest at about 1.30pm between September and March.

UV radiation levels over a summer's day

What is UV radiation?

The sun gives us UV radiation, visible light and heat. UV radiation and the heat from the sun are not the same thing. Many people mistake temperature as an indicator of the UV radiation. Even when the temperature is not hot the UV radiation levels can be dangerously high so temperature is not a good indicator of when you need to protect yourself from the sun’s UV radiation.

There are both risks and benefits of exposure to UV radiation – a balance is required to avoid the risk of skin cancer and at the same time to maintain adequate vitamin D levels. Read more.

What influences the level of UV radiation?

UV radiation levels vary around the globe and over the seasons and times of the day. The level is influenced by:

  • Sun elevation – the higher the sun in the sky, the higher the UV radiation.
  • Latitude – the closer to the equator you are, the higher the UV radiation.
  • Cloud cover – UV radiation levels are higher with clear skies, but can still be high with light cloud cover.
  • Altitude – the higher the altitude you are, the higher the UV radiation.
  • Ozone – the lower the ozone, the higher the UV radiation. Ozone absorbs some of the UV radiation. Ozone levels vary over the year and even across the day.
  • Ground reflection – some surfaces are more reflective eg, snow, sand and water.

New Zealand’s UV radiation

Peak UV radiation levels in New Zealand are around 40% higher than those in North America. New Zealand’s exposure to high levels of UV radiation is mainly because of the position of the sun, the closeness of the sun during summer months, and our unpolluted skies.

In recent years, ozone depletion has increased our exposure to UV radiation. The Antarctic ozone layer hole usually breaks up in early summer that means that, at times, New Zealand is affected by ozone-depleted air travelling over the country. For more information on ozone visit NIWA and the Ministry for the Environment.