Early frost and freeze events in northeast Minnesota: What's normal?
Sep 05, 2025 10:32AM ● By Content Editor
Photo: Michael Held on Unsplash.com
By Laura Durenberger-Grunow - Boreal Community Media - September 5, 2025
After a slow start to the beginning of summer, frost has arrived early in northeastern Minnesota, with some areas seeing it in late August. And while late August and early September frost may seem exceptionally early, historical data show it's not unheard of. According to the National Weather Service (NWS) in Duluth, a freeze (32°F) has occurred a few times historically in the region during late August.
The NWS told Boreal Community Media that a volunteer weather station located ten miles northwest of Gunflint Lake, with about 40 years of data, shows that a freeze has been recorded once in August (August 29, 1976) and several times in early September. The long-term average for the first freeze at this station is September 21. The station has also recorded temperatures in the 30s as early as July 12, 1975, when the temperature dropped to 36°F. The long-term average for the first 36°F date is September 7.
Long-term volunteer observations in the city of Grand Marais, dating back to the 1920s, show slightly different data due to its proximity to Lake Superior. According to the NWS, the earliest recorded freeze was on September 12, 2007, with the long-term average for the first freeze being October 1. Temperatures of 36°F or cooler have been recorded in late August and early September, with the average first date for this occurring on September 20.
By Laura Durenberger-Grunow - Boreal Community Media - September 5, 2025
After a slow start to the beginning of summer, frost has arrived early in northeastern Minnesota, with some areas seeing it in late August. And while late August and early September frost may seem exceptionally early, historical data show it's not unheard of. According to the National Weather Service (NWS) in Duluth, a freeze (32°F) has occurred a few times historically in the region during late August.
The NWS told Boreal Community Media that a volunteer weather station located ten miles northwest of Gunflint Lake, with about 40 years of data, shows that a freeze has been recorded once in August (August 29, 1976) and several times in early September. The long-term average for the first freeze at this station is September 21. The station has also recorded temperatures in the 30s as early as July 12, 1975, when the temperature dropped to 36°F. The long-term average for the first 36°F date is September 7.
Long-term volunteer observations in the city of Grand Marais, dating back to the 1920s, show slightly different data due to its proximity to Lake Superior. According to the NWS, the earliest recorded freeze was on September 12, 2007, with the long-term average for the first freeze being October 1. Temperatures of 36°F or cooler have been recorded in late August and early September, with the average first date for this occurring on September 20.
The National Weather Service issues Frost Advisories for temperatures between 33°F and 36°F, typically on clear nights when the ground loses heat quickly. Data compiled by the Iowa Environmental Mesonet (an organization that collects environmental data from cooperating members with observing networks) shows that while 2025 was the first time since 2009 that a Frost Advisory was issued in August for the region, they have been issued as early as July (in 2013).
On September 4th, 2025, the coldest temperatures in Cook County were 36°F and 37°F, in Grand Marais (the airport) and Schroeder. Temperatures are forecasted to reach the mid-30s again Friday and Saturday evening, before a warmup takes place early next week.
