The humidex is a Canadian invention. It is a measure of how hot we feel. This is based on both high temperature and humidity. Humidity is the amount of water vapor or moisture in the air. In general, higher humidity makes the environment feel hotter. The higher the humidex, the greater the risk of heat stress.

For the general public, the humidex ratings are provided below1:

Graphics outlining humidex ratings


Tips for Workplaces

Monitoring the humidex is part of how workplaces can assess worker risk for heat from the sun every day. If the humidex is 30 or above, your workplace will need to use heat alert or heat warning posters and take recommended actions to prevent heat stress. These actions include drinking more water, and a work/rest cycle regime.

Monitoring the humidex is part of a comprehensive sun safety program.