From NWS
1976: Unseasonably warm weather peaked on September 6-7 with highs generally in the 90s across about the western two thirds of Iowa and some triple digit temperatures reported in the northwest. On the 7th reported highs ranged up to 99 F at Sibley, 100 F at Sioux Center, 101 F at Cherokee, and 104 F at Rock Rapids. Amazingly, a strong cold front swept across the state the following day and by the morning of the 10th frost was reported across the lowlands of Iowa with freezing temperatures at a few locations. In fact at Sibley the high of 99 F on the 7th was followed by a low of 33 F less than three days later on the 10th.

1939: Very hot weather sent the temperature all the way up to 107 F at Glenwood tying the all-time Iowa September mark which had also just been tied the previous day at Logan. The temperature reached 102 F at Des Moines on the 7th making this the latest date on which the temperature has ever reached 100 degrees at that location. Other high temperatures reported around the state included 105 F at Shenandoah, 104 F at Knoxville, and 103 F at Atlantic, Carroll, Little Sioux, and Marshalltown. Amazingly, a month that started with record breaking heat would end with a cold blast that sent the temperature plummeting to 16 F at Sibley on the 30th, only one degree above the all-time Iowa September record low temperature, and produced light snow and sleet at several northern Iowa locations during the last several days of September.

1939: An unseasonably strong heat wave settled across Iowa from September 3-7. Des Moines set its all-time September record with a high of 101 F on the 3rd, reached 100 F on the 6th, then tied the record with 101 F again on the 7th. These are the only occasions of triple digit heat on record at Des Moines in the month of September. Also on the 6th Glenwood reached 107 F, tying the all-time Iowa September record which had also just been tied the previous day at Logan. Other high temperatures on the 7th included 105 F at Shenandoah, 104 F at Knoxville, and 103 F at Atlantic, Carroll, and Marshalltown. Amazingly, a month that started with such record breaking heat would end with a cold blast that sent the temperature plummeting to 16 F at Sibley on the 30th, only one degree above the all-time Iowa September record low temperature, and produced light snow and sleet at several northern Iowa locations during the last several days of the month.

7 September 1955 → An 8-day run of 100 degree heat in Los Angeles, CA finally came to an end, after causing 946 fatalities. 7 September 1970 → At Gibbs High School in St. Petersburg, FL lightning struck the football team. 38 players and 4 coaches were knocked off their feet. 22 were injured and 2 were killed. 7 September 1991 → A wild hailstorm moved across Calgary, Canada. The estimated $400 million in damages set a record insurance loss for any single event in Canadian history. Companies flew in adjusters to handle nearly 80,000 property claims. The 30 minute storm split trees, flooded basements, and broke windows. Raging sewers even blew off manhole covers.

Posted under Weather History