Understanding UV Radiation

The sun sends out different types of radiation – visible light that we see as sunlight, infrared radiation felt as heat and UV radiation that we can't see or feel.

People often confuse infrared and UV radiation. When the temperature is cool it means less infrared radiation but not necessarily less UV radiation.

Types of UV radiation

There are three types of UV radiation, categorised by wavelength: UVA, UVB and UVC. 

  • UVA can cause sunburn, DNA (cell) damage in the skin and skin cancer.
  • UVB causes skin damage and skin cancer. Ozone stops most UVB from reaching the earth's surface.
  • UVC is the most dangerous type of UV. Ozone in the atmosphere absorbs all UVC so none reaches the earth's surface.

Factors affecting levels of UV radiation

Levels of ultraviolet (UV) radiation from the sun change throughout the day, every day, each month, each season, each year, across New Zealand.

The total amount of UV radiation present at a given location is affected by: 

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

To find out more about UV radiation visit NIWA’s website.