A small complex of storms that moved out of northeast South Dakota late Saturday morning caused a concentrated area of straight-line wind damage. The Canby, Minnesota airport measured a wind gust of 72 mph. These type of wind speeds continued across portions of Yellow Medicine and Lac Qui Parle counties where hundreds of trees and power lines were blown down. There was another wind gust of 68 mph at the Department of Transportation road sensor (Near Hanley Falls, MN) that went offline as the gust was recorded.
The worst area occurred in the city of Granite Falls where winds tore open two roofs and allowed water to pour through ventilation ducts into classrooms and hallways, causing hundreds of thousands of dollars in damage to the Yellow Medicine East School District building. The Granite Fun restaurant and golf course also sustained damage with 55 to 60 trees blown down. Due to the extensive damage, the city of Granite Falls declared a state of emergency.
Although wind damage occurred east of Granite Falls, mainly between Sacred Heart to Renville, this storm weakened as it moved eastward toward the western part of the Twin Cities.
A secondary area of storms developed across south central Minnesota during the mid-late afternoon near New Ulm, and produced another area of significant wind damage eastward toward Cannon Falls, and Red Wing. There was a swath of tree damage around Cannon Falls where one house lost its roof, with other having minor roof damage.

Hail in LAC QUI PARLE, MINNESOTA
From 08-AUG-20 12:17:00 to 08-AUG-20 12:17:00 (CST-6)
Location: BOYD
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in YELLOW MEDICINE, MINNESOTA
From 08-AUG-20 11:42:00 to 08-AUG-20 11:55:00 (CST-6)
Location: CANBY ARPT
Magnitude: 60.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several large trees were blown down or uprooted from Canby, and eastward toward St. Leo, and likely farther to the east along Highway 68. Due to the very rural area, and farmland of Yellow Medicine County, damage was isolated.

Thunderstorm Wind in GOODHUE, MINNESOTA
From 08-AUG-20 16:20:00 to 08-AUG-20 16:35:00 (CST-6)
Location: CANNON FALLS
Magnitude: 65.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

There were multiple trees and power lines blown down from southwest of Cannon Falls, through Cannon Falls, and to the east of town.  There were 3-4 houses that had roof damage, one of the houses had their entire roof blown off on Pine Street. One privately owned wind sensor between Cannon Falls and Red Wing had a report of 88 mph, but damage was too isolated for that type of wind severity.

Thunderstorm Wind in YELLOW MEDICINE, MINNESOTA
From 08-AUG-20 11:43:00 to 08-AUG-20 11:43:00 (CST-6)
Location: CANBY ARPT
Magnitude: 63.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Thunderstorm Wind in YELLOW MEDICINE, MINNESOTA
From 08-AUG-20 12:40:00 to 08-AUG-20 12:40:00 (CST-6)
Location: GRANITE FALLS
Magnitude: 60.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A measured wind report from a private weather station.

Thunderstorm Wind in YELLOW MEDICINE, MINNESOTA
From 08-AUG-20 12:15:00 to 08-AUG-20 12:25:00 (CST-6)
Location: HAZEL RUN
Magnitude: 60.00 EG
Property damage: 1.00K
Crop damage: 25.00K
Reported by: Social Media

There was damage in the city of Hanley Falls where a machine shed was blown down, with crop damage around the area. Upstream, and based on radar, isolated crop damage likely occurred from Hazel Run to Hanley Falls, and beyond as the core of the strongest winds moved across this area.

Thunderstorm Wind in YELLOW MEDICINE, MINNESOTA
From 08-AUG-20 12:05:00 to 08-AUG-20 12:15:00 (CST-6)
Location: CLARKFIELD
Magnitude: 60.00 EG
Property damage: 0.00K
Crop damage: 25.00K
Reported by: Newspaper

Several trees were blown down between Clarkfield to Hazel Run. Crop damage was also noted throughout the county.

Thunderstorm Wind in GOODHUE, MINNESOTA
From 08-AUG-20 16:35:00 to 08-AUG-20 16:40:00 (CST-6)
Location: RED WING
Magnitude: 56.00 MG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Emergency Manager

There was lots of wind damage in Red Wing where many trees and branches were blown down, including damage to roofs, and power outages throughout the city. There was a measured wind report from a private weather station of 61 mph west of Red Wing at 1635 LST.

Thunderstorm Wind in RENVILLE, MINNESOTA
From 08-AUG-20 12:55:00 to 08-AUG-20 13:10:00 (CST-6)
Location: MINNESOTA FALLS
Magnitude: 60.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous reports of downed trees and power lines from the eastern part of Granite Falls, eastward along Highway 212 to Sacred Heart. However, the damage became more sporadic eastward toward Sacred Heart.

Thunderstorm Wind in CHIPPEWA, MINNESOTA
From 08-AUG-20 12:45:00 to 08-AUG-20 12:55:00 (CST-6)
Location: GRANITE FALLS
Magnitude: 60.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Numerous trees and power lines were blown down on the north and northeast side of Granite Falls. There was a measured wind gust of 122 mph on a wind farm north of Granite Falls. However, this measurement was taken at 200 feet above the ground.

Thunderstorm Wind in YELLOW MEDICINE, MINNESOTA
From 08-AUG-20 12:23:00 to 08-AUG-20 12:25:00 (CST-6)
Location: HANLEY FALLS
Magnitude: 59.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

A measured wind report from the Department of Transportation wind sensor.

Thunderstorm Wind in YELLOW MEDICINE, MINNESOTA
From 08-AUG-20 12:45:00 to 08-AUG-20 12:55:00 (CST-6)
Location: GRANITE FALLS
Magnitude: 60.00 EG
Property damage: 1.80M
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread wind damage occurred around the city of Granite Falls. Numerous trees, power lines and structural damage occurred in the city with the Yellow Medicine East School District main building sustaining major damage. The winds tore off the heating and ventilation systems on the roofs, opening the duct work to the rain. Water poured through the ventilation system and directly into classrooms, hallways and on equipment.  On the south side of the Minnesota River, the Granite Run golf course suffered significant damage to trees and their local restaurant.

Thunderstorm Wind in RENVILLE, MINNESOTA
From 08-AUG-20 13:10:00 to 08-AUG-20 13:20:00 (CST-6)
Location: SACRED HEART
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Social Media

A few large trees were blown down between Sacred Heart, and Renville, including a large tree that fell on a house in Renville.

Lightning in DAKOTA, MINNESOTA
From 08-AUG-20 16:30:00 to 08-AUG-20 16:30:00 (CST-6)
Location: LAKEVILLE
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

A lightning bolt struck a park shelter where 40 people were attending a birthday party. Three individuals were injured, but with non-life-threatening injuries.