Slightly cooler air is working in to Iowa as highs Thursday and Friday will top out in the 70's. Another, cooler shot of air moves in Friday night. Highs will be in the 60's this weekend, and parts of northern Iowa could see patchy frost Saturday night. A warming trend will begin Monday...
On September 30th in Iowa Weather History:
1961: A storm system produced rain across much of the state that changed to unseasonably early snow as it tapered off across northwestern and northern Iowa. Sioux City reported 0.4 inches of snow making this the earliest occurrence of measurable snowfall on record at that location. Other reported snowfall amounts included 3.0 inches at Swea City, 2.0 inches at Emmetsburg, and a trace at Council Bluffs, Fort Dodge, Hampton, Harlan, and Mason City. Just to the east across far northeastern Iowa heavy rain fell, with accumulations of 3.37 inches at Elkader and 3.35 inches at Fayette setting all-time September single day rainfall records at those locations.
1939: September started out with record breaking heat as Logan and Glenwood tied the all-time Iowa September record with readings of 107 F on the 6th and 7th, respectively, but ended with a blast of cold air that sent the temperature plummeting to 16 F at Sibley on the 30th which is only one degree above the all-time Iowa September record low. Light snow and sleet even fell at some northern Iowa locations in the last few days of the month, with barely measurable snowfall of one or two tenths of an inch recorded at Sheldon and Sibley.
1899: Unseasonably cold weather settled across Iowa on the last five days of September. On the 26th-28th many locations around the state reported frost with a few stations recording freezes on each day. On the 29th and 30th temperatures fell even further, all the way down to 15 F at Mason City on the 30th which tied the all-time Iowa September record established just the previous day at Sheldon and Sibley. Other low temperatures on the 30th included 16 F at Delaware and Monticello, 17 F at Elkader, Toledo, and West Branch, 18 F at Amana, Independence, and Wilton, and 19 F at Clinton, Guthrie Center, Iowa Falls, and Washington. At Des Moines the low of 26 F remains tied for their coldest September temperature on record.