<Li> March 29, 1998: An F4 and an F3 tornado that were part of a larger outbreak tore through the towns of Comfrey and St. Peter . They killed two and caused damage in the millions of dollars in Minnesota's earliest recorded tornado outbreak . </Li> <Li> June 17, 2010: Three EF4 and six EF3 tornadoes were part of 48 twisters that touched down in Minnesota's largest tornado outbreak on record . </Li> <P> Autumn weather in Minnesota is marked by the rapid decrease of severe thunderstorms, dramatic cooling, and eventually the possibility of blizzards . With summer - time heat still prevalent in the southern U.S. and colder air quickly taking hold in Canada, Minnesota can be affected by wide temperature swings in short periods of time . Because of this, the jet stream, which tends to weaken during the summer months, begins to re-strengthen . This leads to quicker changes in weather patterns and increasingly strong storm systems . As autumn moves on, these storm systems bring with them progressively colder air, eventually changing the rain over snow, generally starting in October in the northern part of the state and November in the south . From September to December the average temperature in the state falls by approximately 43 ° F (23 ° C), the largest such temperature swing within any Minnesota season . </P> <P> By late October and November atmospheric dynamics are generally in place to allow storm systems to become very intense . In fact, Minnesota's all - time record low pressure was recorded during autumn on October 26, 2010 . If these powerful storm systems are able to draw enough cold air southward from Canada, they can evolve into powerful blizzards . Some of Minnesota's most memorable winter storm events have occurred during the middle part of the autumn season . On November 11, 1940, the southeast half of Minnesota was surprised by the Armistice Day Blizzard . Temperatures in the 60s ° F (16 ° C) on the morning of November 11 dropped into the single digits (below--12 ° C) by the morning of November 12, bringing with them 27 inches (69 cm) of snow and 60 mph (100 km / h) winds . Known deaths in this blizzard reached 154, 49 of them in Minnesota . On October 31, 1991, much of Minnesota was hit by the Halloween Blizzard . A band of snowfall of 24 + in (60 + cm) fell from the Twin Cities north to Duluth . It was the single largest snowfall ever recorded in many communities across eastern Minnesota . </P>

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