To cite package ‘darksky’ in publications use:

  Rudis B (2017). _darksky: Tools to Work with the 'Dark Sky' 'API'_. R
  package version 1.3.0, <https://github.com/hrbrmstr/darksky>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {darksky: Tools to Work with the 'Dark Sky' 'API'},
    author = {Bob Rudis},
    year = {2017},
    note = {R package version 1.3.0},
    url = {https://github.com/hrbrmstr/darksky},
  }