Humidex Calculator

About this calculator

Humidex is the index Canadian meteorologists use to describe how hot the air feels when humidity is factored in alongside temperature. It's computed as humidex = T + 5/9 × (e − 10), where T is the air temperature and e is the vapor pressure (in hPa) derived from the dew point — high moisture content pushes e up and makes the air feel hotter than the thermometer alone suggests, because sweat evaporates less efficiently.

Environment and Climate Change Canada uses humidex values to trigger heat-warning thresholds (45+ is considered dangerous, 54+ requires immediate action), and forecasters, outdoor-event organizers, and employers with heat-safety policies use it the same way Americans use the related but differently-calculated heat index. Enter the air temperature and dew point (or relative humidity) to get the perceived-heat value.