Relative Humidity and Saturation Vapour Pressure
There are two methods to compute Relative Humidity used in thermofeel and these are used together in some index calculations, such as in the UTCI.
Relative Humidity Percent: https://www.theweatherprediction.com/habyhints/186/
Saturation Vapour Pressure over Water: http://www.thunderscientific.com/tech_info/reflibrary/its90formulas.pdf
How To Use
Saturation Vapour Pressure over Water
The input is 2m temperature in Kelvin. The output is in hPa.
calculate_saturation_vapour_pressure(2m_temperature)
Relative Humidity Percent
The inputs are 2m temperature and dew point temperature in Kelvin. The output is in %.
calculate_relative_humidity_percent(2m_temperature,2m_dew_point_temperature)