Thunderstorms formed in South Central North Dakota just north of the South Dakota border around 3 am on Monday, August 10, 2020. The storm line moved southeast across South Dakota, producing hail to 3″ in diameter and wind gusts as high as 73 mph.

Radar images of the derecho movving

The storms continued southeast into far northeast Nebraska, then turned due east (the path shaped like a hockey stick) and moved across Central Iowa (where the strongest winds occurred), Northern Illinois, far southern Wisconsin, then across Lake Michigan into SW Michigan and Indiana. The remnant line weakened as it moved across Michigan. After midnight, the storms had moved through much of W. Ohio and Kentucky. In the image above, note the bowing echo from 10 am to 5 pm (CDT), when the strongest winds occurred. In general, the strongest winds were along and just north of I-80 in IA and IL. From the Cedar Rapids Gazette (which has excellent coverage of the storm clean-up:

Area hospitals are seeing hundreds of patients in their emergency rooms after this Monday’s storm.

UnityPoint Health-St. Luke’s Hospital in Cedar Rapids saw more than 200 patients on Monday and Tuesday for storm-related injuries and health conditions, according to spokeswoman Sarah Corizzo.

At Mercy Medical Center in Cedar Rapids, emergency room staff have reported nearly 250 visits related to the storm as of Wednesday afternoon. Spokeswoman Karen Vander Sanden said about 60 percent are for acute injuries related to storm cleanup.

The Cedar Rapids hospitals – both still relying on backup generators as of Wednesday afternoon due to the city’s damaged power grid – said most patients are seeking aid for injuries related to the cleanup, including lacerations, injuries from falls and bumps on the head.

Cedar Rapids Fire Chief Greg Smith said officials estimate 8 in 10 residential and commercial properties have sustained damage ranging in severity from minor to severe, sometimes rendering structures uninhabitable or completely collapsed.” Overturned truck on I-380 near Cedar Rapids IA.

Grain bins destroyed by 100 mph winds.

The Iowa Department of Agriculture is estimating that ten million acres of cropland was impacted by Monday’s derecho windstorm. Some analysts are estimating total corn losses from the storm could run as high as 300 to 400 million bushels.

Naig says the damage to grain storage facilities is also a big concern. He estimates “tens of millions of bushels” of commercial grain storage was destroyed or severely damaged, along with millions of bushels of on-farm storage.

Comment from one farmer: “Lots of bins, hog buildings, and other buildings destroyed.
It’s not bad, it’s catastrophic for many. It was like a freaking Cat 2 hurricane moving across our state.” More pics.

Satellite picture shows a lighter color where the corn has been flattened by the strong winds

The satellite pic. above shows the outlined area where you can see a lighter color. This is where the corn has been knocked down by the strong wind. Many grain elevators and bins were damaged or destroyed as well.

Waves crashing over the pier at South Haven, Michigan Monday evening 8 10 20

In Michigan: Generally, from I-94 to the Indiana border, gusts were from 45-70 mph. Much of the area between I-94 and I-96 had gusts of 30-50 mph. Here are some peak gusts from SW Michigan: Benton Harbor 67 mph, St. Joseph 64 mph, Battle Creek 60 mph, Kalamazoo and Jackson 47 mph, Grand Rapids and Lawton 45 mph, S. Haven 43 mph, Lansing 41 mph, Holland 35 mph, Muskegon 33 mph. Wind damage was reported throughout Berrien Co., also at Mattawan, Gobles, Plainwell, Three Rivers, Gull Lake, Decatur, Fair Plain and Grand Beach.

A viewer send us a picture of a trampoline folded in half by the winds near Dorr. Numerous power outages along and south of I-94.

Lightning hit this tree near Ionia

Lightning hit this tree near Ionia. A large branch fell off the tree and you can see how the lightning “explodes” the bark off the tree. You can get hurt by splinters flying off the tree up to 100 feet away from the tree – so don’t stand under or near a tree during a thunderstorm.

Peak winds measured in Iowa during the derecho of August 10 2010

Here’s a time lapse of the drerecho radar. Peak gusts: 112 mph Midway IA, 106 mph Le Grand IA, 100 mph Hiawatha IA, 99 mph Albion IA, 95 mph Marshalltown IA. Here’s a list of peak wind gusts measured in Iowa. Significant building damage occurred in Iowa and Illinois. Twenty schools (most of them?) in Cedar Rapids, Iowa had some damage. One man was killed in Cedar Rapids, when a tree fell on him while he was riding a bicycle. A curfew was in effect in Cedar Rapids. Watch this roof blow off in Chicago. Glad I wasn’t in this truck. Video of the storm and storm damage. Video of the storm and storm damage near Yorkville, Illinois. More storm and damage video.

Pic. from shows one of three trucks tipped over by 85 mph wind gusts near Moline IL

Besides the structural damage, vehicles were flipped on highways, including I-80 and US 30 in Iowa. On US 65, four semis were flipped in a 2 1/2 mile stretch. Three semis tipped over in 85 mph winds near Moline, Illlinois on US 61. Both north and southbound lanes of I-35 were blocked by overturned semis near Des Moines IA. The storm also caused semis to roll over on Highways 17 and 169. Some of those drivers were taken to the hospital with minor injuries. There was one storm fatality. A woman was killed when her trailer flipped over near Fort Wayne IN. Dozens of people were injured by the storms in Iowa and Illinois.

Storm Reports from August 10, 2020

Above is a map of storm reports from Monday August 10. There were 11 confirmed tornadoes (Southern Wisconsin, Northeast Illinois and Northern Indiana). We’re up to 900 reports of +58 mph winds or wind damage and 38 of those are measured wind gusts at or over 75 mph (hurricane force). Gusts hit 92 mph at Dixon, Illinois (where Ronald Reagan grew up). The wind at Dixon blew at 50 mph for more than 20 minutes. More peak gusts: 91 mph at Cedar Point, IL, 85 mph at Lincoln Square (Chicago), 84 mph Plainfield IL, 80 mph Montrose Harbor (Chicago), 80 mph Mendota IL and 75 mph at Lee IL.

Peak winds in Illinois (should be either Moline IL or Davenport IA)

Other peak gusts: 86 mph Moline IL, 72 mph Midway Airport and 72 mph at the water intake in Chicago, 62 mph at O’Hare. Roof damage was reported in Lake Co. IL. Winds hit 53 mph at Racine WI, with wind damage near Kenosha and Lake Geneva WI.

A barn and grain bins “completely gone” in Wakarusa, Indiana where a tornado was confirmed. Another interesting part of the derecho:


A seiche or meteotsunami occurred on Lake Michigan this evening. The water level rose 1.5 FEET at Benton Harbor:

0620 PM     SEICHE           1 N SAINT JOSEPH        42.11N 86.49W  
08/10/2020                   LMZ043             MI   NWS EMPLOYEE       

Here’s time-lapse video of the water rising as the high winds hit near Benton Harbor. Here’s an example of another seiche/meteotsunami. The strong winds from a line of thunderstorms push the water toward the Michigan shore. The water level rises at a fairly rapid rate. You can get caught out on the piers and breakwaters. As the storm passes, the water sloshes back toward the Illinois and Wisconsin shore. As it does, strong currents are possible, moving from the shore to the west and out toward open water. On July 4, 2003, seven people drowned when caught in currents following a severe thunderstorm in St. Joseph Michigan. Here’s a word on the seiche in Chicago back in 1954:

Seiche in Chicago in 1954
Seiche drawing Lake Michigan_1523671404520.gif.jpg
Here’s a graphic on the seiche of 1954

There were 470,000 customers without power in Iowa and another 215,000 in N. Illinois. At 10 am Tuesday, August 11, Marshall County had only 505 customers WITH power (less than 3% of the county) and it’s likely to take a week to get everyone back online. Hundreds of utility poles were snapped or pushed over by the strong winds.

Tornado warnings were issued for a large portion of the Chicago area. There were two reported tornadoes, one in the Rogers Park area north of downtown Chicago. Here’s a time lapse of the storm moving thru Chicago.

Roof partially off the Buccaneers Arena at Urbandale IA. More damage pictures. Boards flew through the air going right through walls. Damage similar to an EF1 or weak EF2 tornado. More pictures.