The Armistice Day Blizzard occurred on November 11th 1940. Now known as Veterans day, this blizzard was not well forecasted. Prior to this storm unusally warm weather was occurring with temperatures in the 50s and 60s, many hunters went out hunting given the warm weather and ideal conditions. Drastic temperature swings occurred with temperatures dropping from the 50s and 60s down into the teens and 20s. The Low moved across Iowa bottoming out at 971mb near Duluth MN. Up to 2 feet of snow fell in Minnesota and drifts were up to 20 feet high. 154 people died, many were the hunters that were caught off guard my the sudden change in the weather.
Article from Minnesota Public Radio
Iowa DNR Article