Several waves of thunderstorms moved across central and southern Minnesota, and into west central Wisconsin between the late afternoon of Wednesday, August 10th, through Thursday morning, August 11th. A few of the storms produced large hail and severe wind gusts as several bow echoes formed. However, the main hazard became the extremely heavy rainfall with bouts of rainfall rates as high as 2 to 3 inches per hour.
By Thursday morning, a large area of 3 to 6 inches of rain fell between Appleton City to Willmar and Hutchinson, southward to Granite Falls and Redwood Falls. Inside this area, there was a smaller area of 6 to 8 inches of rain that fell between Appleton City to Willmar, southward to Olivia. The highest totals were near Olivia and Willmar where two local observations measured 8.78 and 8.09 inches respectfully.
These amounts set the stage for areal and river flooding, with some flash flooding where rainfall rates maximized during the evening near Hutchinson.
This was also the second Mega-rain event this year. The DNR classifies a Mega-rain event as an area that receives six inches of rain and covers more than 1,000 square miles. The last event was July 11-12, 2016 in central Minnesota.  According to the Minnesota DNR, this was the first year (2016), that the state had two mega rainfall events in one year.
The following are some of the higher rainfall amounts during this event that ended Thursday morning, August 11th.
...Anoka County...
Blaine                         3.10
Coon Rapids                 3.02
...Blue Earth County...
Mapleton                      4.50
Mapleton       3.30

...Brown County...
New Ulm                      3.54

...Carver County...
Mayer                          4.91
Norwood/Young America 4.54
...Chippewa County...
Watson 1 NE                 4.93
Laq Qui Parle                4.60
Montevideo                   4.29
...Dakota County...
Burnsville                     3.69
Eagan                          3.24
...Goodhue County...
Wanamingo                  4.93
Zumbrota                     4.75
Red Wing                     4.73
...Hennepin County...
Bloomington                 3.95
Lake Minnetonka           3.70
Maple Grove                 3.48
Minnetonka                  3.37
...Kanabec County...
Mora                           3.23
...Kandiyohi County...
Willmar 5 North           8.09
Willmar                      7.90
Willmar 2 North           7.87
Willmar East                7.23
Pennock                      3.54
...Lac qui Parle County...
Madison                      5.55
Madison                      4.63
Montevideo                  3.75
...Le Sueur County...
Le Center                    3.40
...McLeod County...
Hutchinson                  6.32
Brownton                    5.40
Lester Prairie               4.81
Glencoe                      4.65
Winsted                      4.50
Silver Lake                  4.23
...Meeker County...
Cosmos                       5.48
Manannah                    3.55
Dassel                         3.55
Litchfield                      3.26
...Ramsey County...
St Paul                         3.77
Falcon Heights               3.73
Roseville                      3.49
North St. Paul               3.02
...Redwood County...
Redwood Falls               4.95
...Renville County...
Olivia                        8.78
Lake Lillian                 7.12
Delhi                         6.80
Danube                      6.05
Sacred Heart              5.40
Bird Island                 5.12
Hector                       4.65
...Scott County...
Prior Lake                  3.86
Shakopee                   3.74
Jordan                       3.45
...Sibley County...
Gibbon                       6.70
Arlington                    4.71
Green Isle                  4.48
...Steele County...
Owatonna                    4.38
...Waseca County...
Waseca                       4.58
...Washington County...
Lake Elmo                   3.73
Stillwater                    3.45
Afton                          3.35
Newport                      3.22
Woodbury                    3.16
...Wright County...
French Lake                  3.91
Hanover                       3.60
Big Lake                       3.27
Buffalo                         3.05
Rockford                       3.03.

Thunderstorm Wind in CARVER, MINNESOTA
From 10-AUG-16 19:25:00 to 10-AUG-16 19:27:00 (CST-6)
Location: NORWOOD YOUNG AMERICA
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

There were several trees blown down, two on power lines, and one on a cable/telephone line. The debris was blocking two streets in Norwood Young America.

Heavy Rain in RENVILLE, MINNESOTA
From 10-AUG-16 20:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: BECHYN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A trained spotter measured 7.12 inches of rain near Bechyn.

Thunderstorm Wind in DAKOTA, MINNESOTA
From 10-AUG-16 19:57:00 to 10-AUG-16 20:02:00 (CST-6)
Location: LAKEVILLE
Magnitude: 56.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Social Media

Several large trees blew down in north Farmington, some that caused damage to homes. There were also pictures on social media of large tree limbs blown down near Lake Marion.

Flash Flood in MCLEOD, MINNESOTA
From 10-AUG-16 19:00:00 to 10-AUG-16 21:00:00 (CST-6)
Location: HUTCHINSON
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Local law enforcement official closed several roads in Hutchinson due to flooding, and some of the roads had up to 9 inches of flowing water. There was also a city pool that was under construction that received damage to the point that it would have to be torn out and new construction started. The concrete was inundated with water that caused the cement to come apart from the plumbing and silt washed under the concrete floor. There were also a few rural gravel roads that were washed out that had some damages.

Hail in KANDIYOHI, MINNESOTA
From 10-AUG-16 15:10:00 to 10-AUG-16 15:10:00 (CST-6)
Location: PRIAM
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in KANDIYOHI, MINNESOTA
From 10-AUG-16 15:36:00 to 10-AUG-16 15:36:00 (CST-6)
Location: PENNOCK
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in WASECA, MINNESOTA
From 10-AUG-16 18:25:00 to 10-AUG-16 18:25:00 (CST-6)
Location: JANESVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Heavy Rain in RENVILLE, MINNESOTA
From 10-AUG-16 20:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: BIRD ISLAND
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A trained spotter measured 5.12 inches of rain south of Bird Island.

Heavy Rain in TODD, MINNESOTA
From 10-AUG-16 15:00:00 to 11-AUG-16 03:00:00 (CST-6)
Location: PILLSBURY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A trained spotter measured 5.32 inches of rain near Pillsbury.

Heavy Rain in MCLEOD, MINNESOTA
From 10-AUG-16 18:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: BROWNTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A trained spotter measured 5.40 inches of rain in Brownton.

Heavy Rain in RENVILLE, MINNESOTA
From 10-AUG-16 20:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: SACRED HEART
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

An individual measured 5.40 inches of rain in Sacred Heart.

Heavy Rain in MEEKER, MINNESOTA
From 10-AUG-16 18:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: COSMOS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A trained spotter measured 5.48 inches of rain in Cosmos.

Heavy Rain in LAC QUI PARLE, MINNESOTA
From 10-AUG-16 15:00:00 to 11-AUG-16 03:00:00 (CST-6)
Location: MADISON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A trained spotter measured 5.55 inches of rain in Madison.

Heavy Rain in RENVILLE, MINNESOTA
From 10-AUG-16 20:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: DANUBE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A trained spotter measured 6.05 inches of rain northwest of Danube.

Heavy Rain in MCLEOD, MINNESOTA
From 10-AUG-16 18:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: HUTCHINSON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A trained spotter measured 6.16 inches of rain in Hutchinson.

Heavy Rain in RENVILLE, MINNESOTA
From 10-AUG-16 20:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: OLIVIA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A trained spotter measured 6.54 inches of rain in Olivia.

Heavy Rain in SIBLEY, MINNESOTA
From 10-AUG-16 20:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: GIBBON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

An individual measured 6.70 inches of rain in Gibbon.

Heavy Rain in RENVILLE, MINNESOTA
From 10-AUG-16 20:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: BIRD ISLAND
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A trained spotter measured 7.12 inches of rain northeast of Bird Island.

Heavy Rain in KANDIYOHI, MINNESOTA
From 10-AUG-16 17:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: WILLMAR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A trained spotter measured 7.23 inches of rain in Willmar.

Heavy Rain in KANDIYOHI, MINNESOTA
From 10-AUG-16 17:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: WILLMAR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A trained spotter measured 7.87 inches of rain north of Willmar.

Heavy Rain in KANDIYOHI, MINNESOTA
From 10-AUG-16 17:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: WILLMAR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A trained spotter measured 7.90 inches of rain southwest of Willmar.

Heavy Rain in KANDIYOHI, MINNESOTA
From 10-AUG-16 17:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: WILLMAR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A trained spotter measured 8.09 inches of rain north of Willmar.

Heavy Rain in RENVILLE, MINNESOTA
From 10-AUG-16 20:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: OLIVIA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

An individual measured 8.78 inches of rain north of Olivia.

Heavy Rain in MCLEOD, MINNESOTA
From 10-AUG-16 18:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: HUTCHINSON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A measured rainfall report of 6.33 inches occurred in Hutchinson.

Flash Flood in HENNEPIN, MINNESOTA
From 10-AUG-16 19:30:00 to 10-AUG-16 21:30:00 (CST-6)
Location: EDINA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A local weather observer reported that parts of Highway 62, at Penn Avenue were completely underwater during the height of the heavy rainfall event.

Flash Flood in HENNEPIN, MINNESOTA
From 10-AUG-16 19:30:00 to 10-AUG-16 21:30:00 (CST-6)
Location: HOPKINS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Water was covering Westbrooke Way near Nine Mile Creek, west of Highway 169 in Hopkins.

Flash Flood in RENVILLE, MINNESOTA
From 10-AUG-16 19:00:00 to 10-AUG-16 21:00:00 (CST-6)
Location: OLIVIA MUNI ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Nearly five inches of rain fell in Olivia between 6 - 8 PM CST. These extreme rainfall rates and resultant flooding caused several vehicles to stall in water on low lying streets in Olivia.  One person needed the fire department to be rescued. The city administrator in Olivia says at least 100 homes had been impacted by flood-related damage.

Flash Flood in SCOTT, MINNESOTA
From 10-AUG-16 20:30:00 to 10-AUG-16 22:30:00 (CST-6)
Location: PRIOR LAKE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

There was eight inches of water along Eagle Creek Ave Southeast in Prior Lake. It affected traffic on the northbound side of the bridge between Upper and Lower Prior Lake.

Thunderstorm Wind in KANABEC, MINNESOTA
From 10-AUG-16 17:38:00 to 10-AUG-16 17:40:00 (CST-6)
Location: MORA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

There were several trees and large tree branches that blew down in Mora. One was 10 inches in diameter and was uprooted on South Union Street.

Thunderstorm Wind in KANABEC, MINNESOTA
From 10-AUG-16 17:25:00 to 10-AUG-16 17:26:00 (CST-6)
Location: OGILVIE
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several large trees were blown down northwest of Mora. A trained spotter had one of his neighbors 18 diameter white ash fall on his property.

Flash Flood in KANDIYOHI, MINNESOTA
From 10-AUG-16 18:00:00 to 10-AUG-16 21:00:00 (CST-6)
Location: WILLMAR
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several rounds of very heavy rainfall caused significant flooding in the town of Willmar. The first two rounds of heavy rainfall added up to locally 4-6 inches by 9 PM CST. Significant runoff caused some roads to close with basement flooding.

Flood in KANDIYOHI, MINNESOTA
From 10-AUG-16 21:00:00 to 11-AUG-16 06:00:00 (CST-6)
Location: PENNOCK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Local Official

A third round of heavy rainfall added up to 8-10 inches by early Thursday morning, August 11th. The runoff from the rainfall caused substantial damage to an estimated 800 to 1,000 homes in Willmar alone. The flood water also damaged businesses and parks. The city's municipal infrastructure, such as roads and utilities, were spared the worst damage, which is why Willmar did not declare a disaster.

Thunderstorm Wind in CARVER, MINNESOTA
From 10-AUG-16 19:50:00 to 10-AUG-16 19:50:00 (CST-6)
Location: NORWOOD YOUNG AMERICA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

A few 8 inch diameter tree branches were blown down in Norwood Young America.