To cite the 'humidity' package in publications use:

Jun Cai (2016). humidity: An R Package for Calculating Water Vapor Measures from Temperature and Relative Humidity. R package version 0.1.1.

Corresponding BibTeX entry:

  @Manual{,
    title = {humidity: An R Package for Calculating Water Vapor
      Measures from Temperature and Relative Humidity},
    author = {Jun Cai},
    year = {2016},
    note = {R package version 0.1.1},
    url = {https://github.com/caijun/humidity},
  }