Heat index
At high temperatures, the level of relative humidity needed to make the heat index higher than the actual temperature is lower than at cooler temperatures. For example, at approximately 27 °C (80 °F), the heat index will agree with the actual temperature if the relative humidity is 45%, but at about 43°C (110°F), any relative-humidity reading above 17% will make the Heat Index higher than 43°C (110 °F).