Among all the historical climate records throughout the Pioneer Era perhaps the most unusual is March of 1843. The mean temperature for the month at Ft Snelling was just 4.7 degrees F. For frame of reference the average March temperature in the Twin Cities for 1971-2000 was 32.1 degrees F. So, 1843 brought a monthly departure of negative 27.4 degrees F from the modern "normal." The mean temperature of 4.7 degrees F in March of 1843 would rank among the top 12 coldest months of January in the Twin Cities modern record.
The soldiers at Ft Snelling reported 20 mornings with below 0 degrees F temperatures in March 1843, and as late as the 26th it was -15 degrees F. There were six snow storms during the month, but snow depth was not noted. It was reported that river and lake ice was extremely thick at the end of the month. Lake Pepin was not ice-free that year until May 20th.