"Station: Salem, IL". U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991–2020). National Oceanic and Atmospheric Administration. Archived from the original on July 25, 2021. Retrieved July 24, 2021.
"Station: Salem, IL". U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991–2020). National Oceanic and Atmospheric Administration. Archived from the original on July 25, 2021. Retrieved July 24, 2021.