Welcome to The New Summer Simmer Index®

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

Online-Calculator: Calculate Summer Simmer Index
Table in °Fahrenheit: The New Summer Simmer Index

• 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.