Overall the pattern and antecedent environment were not extremely conducive to severe weather with an environment of around 1000 J/kg and effective shear under 30 kts, but it did not rule out the potential for periods of heavy rainfall.
High pressure ridging was situated over the SW United States, leaving much of the Upper Midwest along the ring of fire, or northwesterly flow/transition from ridge to trough. A shortwave was moving through the upper level flow, initiating weak convection during the evening and overnight hours of the 7th into the 8th, which was then aided by the nocturnal low level jet. Severe weather was negligible, though several rural roads were eventually closed due to heavy rainfall and localized flooding. With storms initiating and propagating over similar areas much of the night, total heavy rainfall of up to 5.6 inches was reported, with most reports in the 2 to 4 inch range.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 06:00:00 to 08-JUN-18 06:00:00 (CST-6)
Location: MASON CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Coop observer recorded heavy rainfall of 2.45 inches over the last 24 hours.

Heavy Rain in WORTH, IOWA
From 07-JUN-18 06:00:00 to 08-JUN-18 06:00:00 (CST-6)
Location: NORTHWOOD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Coop observer recorded heavy rainfall of 2.17 inches over the last 24 hours.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 07:00:00 to 08-JUN-18 07:00:00 (CST-6)
Location: MESERVEY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported heavy rainfall of 3.50 inches over the last 24 hours.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 21:15:00 to 08-JUN-18 09:45:00 (CST-6)
Location: MASON CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 5.1 inches from last night and this morning.  This is a delayed report.

Flood in CERRO GORDO, IOWA
From 08-JUN-18 12:40:00 to 09-JUN-18 09:59:00 (CST-6)
Location: CLEAR LAKE LAKE
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 500.00K
Reported by: Law Enforcement

Cerro Gordo County Sheriff's Department reported several roads covered by water across the county.

Heavy Rain in CERRO GORDO, IOWA
From 08-JUN-18 02:20:00 to 08-JUN-18 07:40:00 (CST-6)
Location: FREEMAN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported heavy rainfall of 3.65 inches from about 3:20 am through 8:25 am. The 24 hour total through 8:25 am was 4.06 inches.

Flash Flood in WORTH, IOWA
From 08-JUN-18 09:20:00 to 08-JUN-18 12:50:00 (CST-6)
Location: MANLY
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 100.00K
Reported by: Law Enforcement

Law enforcement reported several county gravel roads closed around the town of Manly, with one road washed out south of Highway 9 on Mallard Ave.

Heavy Rain in WORTH, IOWA
From 07-JUN-18 20:45:00 to 08-JUN-18 07:50:00 (CST-6)
Location: MANLY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported heavy rainfall of 5.00 inches.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 21:15:00 to 08-JUN-18 07:51:00 (CST-6)
Location: MASON CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported heavy rainfall of 4.70 inches, and this is an updated total from a 6:15 am storm report of 3.75 inches.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 21:30:00 to 08-JUN-18 02:30:00 (CST-6)
Location: MASON CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A river gauge location along the Winnebago River recorded heavy rainfall of 2.13 inches.

Heavy Rain in WORTH, IOWA
From 07-JUN-18 20:45:00 to 08-JUN-18 03:20:00 (CST-6)
Location: GRAFTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public recorded heavy rainfall of 2.34 inches from a home weather station.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 21:45:00 to 08-JUN-18 03:31:00 (CST-6)
Location: HURLEY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public recorded heavy rainfall of 3.01 inches from a home weather station.

Heavy Rain in WORTH, IOWA
From 07-JUN-18 20:45:00 to 08-JUN-18 08:35:00 (CST-6)
Location: GRAFTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported heavy rainfall of 3.18 inches.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 21:15:00 to 08-JUN-18 10:42:00 (CST-6)
Location: MASON CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Local media, KIMT, reported heavy rainfall of 5.6 inches.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 21:00:00 to 08-JUN-18 08:00:00 (CST-6)
Location: MASON CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 5.3 inches from 10 pm on the 7th through 9 am on the 8th.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 21:30:00 to 08-JUN-18 03:32:00 (CST-6)
Location: BURCHINAL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public recorded heavy rainfall of 2.95 inches via a home weather station.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 21:15:00 to 08-JUN-18 05:15:00 (CST-6)
Location: MASON CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported heavy rainfall of 3.75 inches via social media.

Heavy Rain in CERRO GORDO, IOWA
From 07-JUN-18 06:00:00 to 08-JUN-18 06:00:00 (CST-6)
Location: SWALEDALE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 3.05 inches.