To prevent adverse health effects, the World Health Organization promotes the diffusion of the ultraviolet radiation index (UVI), with messages promoting precautionary behaviors, through a scale that considers extreme UVI values to be larger than 11.0. This scale came from a proposal from Canada, a country with a mostly light-skinned population, which experiences maximum UVI values up to 10.0. A modified scale was proposed, adapted to the skin types and the UVI levels in South America, which considers extreme values larger than 16.0. The records from 2010 to 2014 indicated that UVI is frequently larger than 11.0 (40.0-76.1% of the days per month) in Quito (Ecuador). The number of days per month with levels larger than 16.0 varied between 0.7% and 32.0%. We found that the maximum UV index levels do not occur necessarily around the local solar noontime. As the basis for a self-warning system in Quito and based on their skin type and UVI levels, people should know the exposure time before damage can take place. The Tropospheric Emission Monitoring Internet Service (TEMIS) computed the UVI at local solar noontime and under clear-sky conditions. The records from 2010 to 2014 were congruent with the corresponding TEMIS values. We did not identify any trend of the daily TEMIS UVI values during 1979 to 2018, which, used as a proxy, suggested the real UVI levels in Quito during 2010 to 2018 varied in a range similar to 1979-2009.