From NWS
1988: A very hot and dry summer intensified in late June with about half of the observing stations in Iowa reporting triple digit heat on the 20th, including Dubuque which incredibly reached 100 F for the first time since 1941. The highest reported temperatures included 102 F at Carroll, Charles City, Sioux City, and Waterloo, and 104 F at Jefferson and Red Oak. Remarkably temperatures would rise even further the following day.

1974: Just two days after an F4 tornado produced fatalities in central Iowa another killer tornado struck northern Clinton County, resulting in one death and 20 injuries. Widespread severe weather spread from northern into eastern Iowa with large hail, wind gusts to 75 to 90 mph, and flash flooding occurring from Kossuth, Winnebago, and Hancock counties over to Allamakee, Dubuque, Cedar, and Lee counties.

1908: A severe thunderstorm cut a path across far northeastern Iowa producing heavy rain, strong winds, and very large hail in a damage swath around 15 miles wide extending from Cresco to McGregor. Many animals were drowned or killed by the hail and in some locations the stones were large enough to break the siding on houses. At Decorah an observer noted that all crops were completely destroyed within the hail swath and that “the foliage was entirely stripped from all trees and plants”. Several barns and outbuildings were also blown down by the strong straight-line winds. At South McGregor a severe flash flood washed logs from the lumber yards and “any loose objects that would float” into the Mississippi River and deposited 3 to 4 feet of mud in many businesses and homes.

20 June 1928 → A farmer from Greensburg, KS looked up into the heart of a tornado. He described it as “rotating clouds lit with constant flashes of lightning and a strong gassy odor with a screaming, hissing sound.” 20 June 1957 → An F5 tornado in North Dakota caused great destruction in Fargo. Over 1300 homes were destroyed or damaged over a 9 mile path. There were 10 fatalities and 103 injuries. 20 June 1972 → From the 20th to the 25th former Hurricane Agnes, in combination with a mid-latitude low pressure area, deluged Pennsylvania and New York with torrential rains resulting in one of the most costly floods in U.S. history. In the Middle Susquehanna Valley of Pennsylvania, rainfall amounts were generally 8 to 12 inches, with up to 19 inches in Schuylkill County. At Wilkes-Barre, the dike was breached, destroying much of the town. Flooding resulted in 117 deaths and $3.1 billion in damage.

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