From NWS
1972: Slow moving morning thunderstorms dropped 5.50 inches of rain at Sioux City, setting the all-time daily rainfall record at that location. Further east rainfall amounts included 4.63 inches at Sac City and 3.45 inches at Humboldt.

1936: The hottest month on record in Iowa continued as the temperature reached 104 F at Des Moines making it a record 15th consecutive day of triple-digit heat. The next-longest such streak is only 8 days which occurred in July of 1934. Other high temperatures reported around the state on this day included 109 F at Atlantic, 110 F at Onawa, and 111 F at Denison, Logan, and Rock Rapids.

This Day in National/World Weather History …

17 July 1934 → One of the worst heat waves in the nation’s history began. During the last two weeks of July, extreme heat claimed 679 lives in Michigan, with 300 of them in Detroit alone. 17 July 1972 → South America’s coldest temperature, -38 degrees, was attained at San Juan, Argentina. 17 July 1995 → 739 people in Chicago died in a record heat wave that lasted for 6 days, ending today. 141 people in nearby southeast Wisconsin succumbed to the heat as well. 17 July 2001 → Lightning struck a Minnesota National Guard field training site located in Camp Ripley. Nearly two dozen Marine Corps reservists were sent to hospitals. Most were released after treatment.

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