"Station: Duluth, MN". U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991–2020). National Oceanic and Atmospheric Administration. Retrieved June 22, 2021.
"Station: Superior, WI". U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991-2020). National Oceanic and Atmospheric Administration. Archived from the original on January 18, 2024. Retrieved June 13, 2021.
Freudenheim, Milt (December 11, 2005). "The Next Retirement Time Bomb". The New York Times. Archived from the original on May 18, 2021. Retrieved February 21, 2017.
Official records for Duluth were kept at downtown from August 1871 to May 1941, and at Duluth Int'l since June 1941. For more information, see ThreadEx.
"The Duluth Rose Garden". Public Gardens of Minnesota. University of Minnesota. Archived from the original on April 23, 2017. Retrieved April 23, 2017.
"Station: Superior, WI". U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991-2020). National Oceanic and Atmospheric Administration. Archived from the original on January 18, 2024. Retrieved June 13, 2021.
Freudenheim, Milt (December 11, 2005). "The Next Retirement Time Bomb". The New York Times. Archived from the original on May 18, 2021. Retrieved February 21, 2017.
"The Duluth Rose Garden". Public Gardens of Minnesota. University of Minnesota. Archived from the original on April 23, 2017. Retrieved April 23, 2017.