The Summer Simmer Index refers to the perceived temperature based on the measured air temperature and relative humidity.

In contrast to the heat index or humidex, it refers to the perceived heat at night and represents a factor for discomfort.

• 21.3 – 25 °C Somewhat cool. Most people feel comfortable.
• 25 – 28.3 °C Optimal. Almost everyone feels comfortable.
• 28.3 – 32.8 °C Somewhat hot. Most people feel comfortable.
• 32.8 – 37.8 °C Hot. Partially uncomfortable.
• 37.8 – 44.4 °C Moderately hot. Uncomfortable. Risk of heat stroke.
• 44.4 – 51.7 °C Very hot. Risk of heat stroke.
• above 51.7 °C Extremely hot. Very high risk of heat stroke.