Threaded Climate Extremes
Weaving Today’s Climate Extremes with Past Records

ThreadEx, which stands for Threaded Extremes, takes the maximum and minimum temperature, and the daily total precipitation recorded at National Weather Service Automated Surface Observing Stations (ASOS) and pieces it together with other historical data nearby to create a single, long-term set of daily weather information dating back well over a hundred years.

In the Northland, this includes the official climate sites of International Falls, MN and Duluth, MN. Beginning in August 2009, the extreme maximum and minimum temperatures, as well as the record daily precipitation/snowfall records will be from the threaded data set. See below for an explanation for each site.

International Falls, MN

Threaded Data Period of Record:   1906 - Current (1926-1939 no data)

Station History:
Prior to 1927, there was a military base not far from where the current International Falls Airport resides. The military base took periodic weather readings from 1895 to 1899 and again from 1906 to 1926. However, there are significant gaps in the records during this time as well as inconsistencies with the modern data since the thermometer rested on a roof top and weather recording procedures were different at that time. 

There is no precipitation data in the International Falls area from 1927 to 1939. For temperature extremes, there is no data from 1927 to 1947.

In November 1939, weather observers began recording daily precipitation values at the International Falls Airport, located in International Falls, MN.  Several years later, in 1947, the weather observers began taking temperature readings that now provide information for the minimum and maximum daily records at International Falls.
More Information About this Station

Duluth, MN
Threaded Data Period of Record: November 1871 to Current
Station History:
Duluth, MN was one of the nation's first weather observing sites.  Weather observations from 1871 to 1959 were taken at the origonal National Weather Service office located in downtown Duluth, on the shore of western Lake Superior.

In 1940, the office was moved 6 miles up steep terrain, an elevation change of around 600 ft, to the Duluth Airport. Between the years of 1941 and 1959, weather observations were taken at both locations.  Since 1959, the official climate observations for Duluth have been taken at the National Weather Service Office located near the Duluth International Airport.

Although weather records exist from the original observing site in downtown Duluth, the threaded dataset only looks at the weather observations taken at the Duluth Airport during the overalp period.  

Snowfall was not part of the daily climate record until 1875. Thus, the All-Time snowfall records are from 1875 to present, whereas the Airport snowfall records are from 1943 to present. The snowfall records also have an overlap from 1943-1959 where snowfall was measured at both locations.

More Information About this Station
Learn more about the background into Threaded data and the ThreadEx project. is the U.S. government's official web portal to all federal, state and local government web resources and services.