<P> The 2007 Midwest flooding, which affected the hilly Driftless area of southeast Minnesota was the result of a training pattern of storms mixing warm moist air from Tropical Storm Erin with cooler Canadian air, resulting in record 24 - hour rainfall totals of up to 17 inches (432 mm), with a similar flooding event in 2010 as a result of the remnants of tropical storm Georgette in the eastern Pacific and Hurricane Karl in the Gulf of Mexico . </P> <P> During a Minnesota summer, heat and humidity predominate in the south, while warm and less humid conditions are generally present in the north . A main feature of summer weather in Minnesota and the Midwestern United States as a whole is the weakening of the jet stream, leading to slower movement of air masses, a general increase in the stability of temperatures, and less wind . The strong wind that does blow almost always comes from the south, bringing in warm temperatures and humidity . These humid conditions and a jet stream that has pushed into the northern parts of the U.S. initiate thunderstorm activity 30--40 days per year . </P> <P> Daily average summer temperatures in Minnesota range from the low 70s (22 ° C) in the south to the mid 60s ° F (19 ° C) in the north . Because summer time air masses are not as volatile as in the winter, daily high and low temperatures rarely vary more than 15 degrees (7 ° C) either side of normal . While summertime around much of the country means long stretches of hot and humid weather, Minnesota is located far enough north where periods of cooler, drier polar air frequently move in behind polar fronts dropping south from Canada . The polar air typically does not linger very long however and is quickly replaced by the warmer and more humid air from the Gulf of Mexico again . The cool, dry polar air colliding with hot and humid summertime air keep the threat of thunderstorms and tornadoes in Minnesota through July and August . Northern Minnesota is considerably cooler and less humid than southern Minnesota during the summer months . For example, Duluth's annual average temperature and dew point are 6 degrees (3.4 ° C) cooler than Minneapolis' . </P> <P> July is the hottest month in Minnesota statewide and is usually the month when the peak heat waves occur . In July 1936, Minnesota and the rest of the Midwest suffered through its most severe heat wave on record . Most of the state was engulfed in 100 ° F (38 ° C) temperatures for several days in a row, and Minnesota's all - time record high temperature of 114 ° F (46 ° C) was equaled during this stretch . This heat wave was also responsible for the Twin Cities' all - time record high of 108 ° F (42 ° C), as well as the all - time record high of several other cities across the state . </P>

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