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1979: Robert Steadman publishes his seminal paper introducing the calculation of the heat index with values given in his Table 2. Unfortunately, no values are calculated for extreme heat and humidity.
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2022: Yi-Chuan Lu and David Romps publish a paper that calculates the heat index for all combinations of temperature and humidity. Associated with this publication is the release of R and Python code for calculating the heat index.
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2025: Yi-Chuan Lu and David Romps release the
heatindex
package on CRAN and PyPI with two functions: theheatindex
function, which calculates the heat index 10,000 times faster than the previously released R and Python code (based on this paper), and thewetbulb
function, which calculates the wet-bulb temperature using the accurate Rankine-Kirchhoff framework (based on this paper).