UV Index Graph

The graph above shows a running real-time value of UV Index (Y axis) against Day/Time (X axis). The different background colours correspond to each of the UV Index exposure categories:

UV IndexExposure CategoryProtection Required
1, 2LowNone. You can safely stay outside.
3, 4, 5ModerateTake care during midday hours and do not spend too much time in the sun unprotected.
6, 7High Seek shade during midday hours, cover up and use sunscreen.
8, 9, 10Very HighSpend time in the shade between 10am and 4pm. Shirt, sunscreen and hat essential.
11+ExtremeAvoid being outside during midday hours. Shirt, sunscreen and hat essential.

During night-time hours, the UV Index is zero. At dawn the UV Index gradually rises until the solar noon hour, when the sun is at its highest point in the sky. Thereafter, UV Index values gradually fall off back to zero by dusk. Under clear skies, the rise and fall of UV very much mirrors a ‘bell curve’. However, scattered cloud cover impacts UV Index values, causing fluctuations in the curve as the cloud comes and goes. Passing clouds temporarily reduce the UV Index, while completely overcast skies will tend to reduce UV values throughout the whole day.

Note that forecast values provided are under clear sky conditions. During a full sunshine day, the observed value should match very well with the forecast value. However, if there is a lot of cloud or overcast skies, the curve will generally be depressed with the maximum forecast value unlikely to be reached due to the reduction of UV reaching the ground by the extensive cloud cover.

The equipment required to record the UV Index is called a UV radiometer. Kipp & Zonen, a Dutch company, is the specialist in the measurement of solar and sky radiation, and are the world leader in this type of equipment. For more information on their products and UV monitoring please navigate to http://www.kippzonen.com/News/128/UV-Monitoring#.VVUDQfBBm3Y

Bermuda is very fortunate to have this equipment (http://www.kippzonen.com/Product/28/UVS-E-T-UV-Radiometer) located at the Bermuda Weather Service. Bermuda Cancer and Health Centre are kindly sponsoring the project, while the Bermuda Weather Service are operating and maintaining the equipment, and disseminating the data to the community via this website and cable television channels, WOW and CV. The Bermuda Weather Service is operated by CI2 Aviation Bermuda Ltd on behalf of the Department of Airport Operations (DAO). Both CI2 Aviation Bermuda Ltd and the DAO are in full support of this very valuable community initiative.

NOTE: Information for the clear sky UV Index forcast can be found here.