The .R file contains a function to calculate the heat index based on the National Weather Service modified Rothfusz regression, including the adjustments. I also calcualted the apparent temperature using the Kalkstein and Valimont 1986 equation.

Input could be Fahrenheit/Celsius, dew point temperature/relative humidity; dew point temperature/relative humidity transformation is based on August-Roche-Magnus approximation.

Default output is a data.frame of four columns: heat index in Fahrenheit/Celsius and apparent temperature in Fahrenheit/Celsius, all replaced by air temperature when below 68 Fahrenheit.

To note, if daily maximum heat index is needed and only daily data available, we could use 1) daily maximum ambient temperature + daily minimum relative humidity (RH decreases as T increases when water content remains the same); 2) daily maximum ambient temperature + daily maximum dew point temperature (DP remains constant as long as the water content remains the same); and 3) daily maximum ambient temperature + daily average dew point temperature (DP is more stable than ambient temperature). The first and third calculations are more conservative as they do not assume that the maximum water content and ambient temperature occured at the same time. However, the first calculation should only be used when RH is the original data provided--if only DP is avaiable, the first calculation should not be used because the transformation from DP to RH in the codes used ambient temperature (daily maximum). These are just a few possible choices and the use of RH in health study is not recommended by previous studies (Baldwin et al. 2023, and Davis et al. 2016). Example of using the first method.

Please contact Chen Chen ([email protected]) if have questions/suggestions.