Summer Simmer Index

Not Reviewed
Equation / Last modified by KurtHeckman on 2018/07/10 16:20
`SSI = `
rklarsen.Summer Simmer Index

The Summer Simmer Index calculator computes the Summer Simmer Index based on the air temperature and relative humidity.

INSTRUCTIONS: Choose units and enter the following:

  • (t) This is the air temperature.
  • (RH) This is the relative humidity.

Summer Simmer Index (SSI): The calculator returns the index in degrees Fahrenheit.  However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

The formula for the Summer Simmer Index is:

     SSI = 1.98(Tf - (0.55 - 0.0055(RH))(Tf-58)) - 56.83 


  • SSI is the Summer Simmer Index  in degrees Fahrenheit
  • Tf is the temperature in degrees Fahrenheit
  • RH is the relative humidity expressed as an integer.

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