The UV Index and Ozone

A chart showing the exposure risks of the UV index. See long description below.

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Table 1. Exposure Risks of the UV Index
ColourExposure CategoryUV Index
GreenLow0 - 2
YellowModerate3 - 5
RedVery High8-10

Welcome to Environment Canada's gateway for the ultraviolet (UV) Index and ozone program. These pages will allow you to find information on UV Index forecasts, namely: where to find the information, how to use it, what today's UV Index values are, the science of UV and ozone, and lastly, information on how to protect yourself against harmful UV rays.

Ultraviolet (UV) rays are the sun rays that can cause sunburn. Long-term exposure to UV rays has been associated with skin aging, eye cataracts, weakening of the immune system, and skin cancer.

The amount of UV that you receive depends on both the strength of the sun's rays (measured by the UV index) and the amount of time you spend in the sun. The higher the UV Index number, (the UV Index is a 0 - 11+ scale) the stronger the sun's rays, and the greater the need to take sun safety precautions.

Sun protection tips include:

  • Reducing your time in the sun (particularly between 11:00 a.m. and 3:00 p.m., from April to September),and seek shade when outdoors.
  • Cover up by wearing a broad-rimmed hat, a shirt with long sleeves, and wrap-around sunglasses.
  • Use sunscreen (with both UVA and UVB protection) with a sun protection factor (SPF) of 15 or higher.
  • Listen for Environment Canada's UV Index which is included in your local weather forecast (when it is forecast to reach 3 or higher (moderate) during the day).
  • Learn more about recommended sun protection actions for different values of the UV Index.
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