An official wind gust of 128 km/h (80 mph) was recorded at the Killarney weather station on the north shore of Lake Huron.
At the nearby Jack Garland Airport, the wind measuring instrument snapped off before the peak gusts could be recorded; some estimates put them higher than 180 km/h (111 mph).
Within the district, the communities of West Nipissing, Callander, East Ferris and Mattawa, all about five hours north of Toronto, declared states of emergency in the wake of the storm as roadways in the area were blocked by felled trees and power was out throughout the region.
Through the next two hours the storm entered the Upper Ottawa Valley affecting places in Renfrew County such as Barry's Bay, Deep River, Cobden, Petawawa and Pembroke.
At times, the storm moved at a forward speed of 100–120 km/h (65-75 mph) but had slowed down somewhat when it entered the Pontiac region of western Quebec.
In the Upper Gatineau north of the National Capital Region, several houses and cottages were damaged and scores of trees were snapped by winds in excess of 90 km/h (55 mph).
Northwest of that town in Grand-Remous, several trailers in a park were heavily damaged or destroyed by the force of the winds but no injuries were reported there.
Additional damage was reported in the Papineau region further east as well as in Mont-Laurier and the popular tourist village of Mont-Tremblant in the Upper Laurentians.
During the rest of the late evening, the storm weakened as it travelled through southern Quebec and eastern Ontario, but still brought lightning to the Laurentians north of Montreal.
The following day, the remnants of the derecho reformed over parts of New England, including Maine, with effects less severe than the original cluster.
Hydro-Québec estimated that 145,000 of their customers lost power but separate storms in the areas around Rouyn-Noranda, Val-d'Or, Montreal, Trois-Rivières and Quebec City contributed to some of the outages.
[3] Final damage assessments from this destructive storm are unlikely ever to be fully known, in part because of the remoteness of large portions of the affected area.
The precise injury count and death toll are also uncertain, again due to inaccessibility to parts of the region, especially with trees blocking so many remote roads.
Environment Canada investigated areas with heavy damage to ascertain whether tornadoes touched down, particularly on the Manitoulin Island[4] and in Larder Lake, near Kirkland Lake but, at this stage, almost all damage reports are straight-line in nature and radar imagery favours a classic 'progressive derecho storm' with winds of up to and possibly exceeding 200 km/h (120 mph) at its peak, possibly with embedded tornadoes.
There were dozens of reports of significant wind or tornado damage, especially in Michigan but also in southern Ontario, Wisconsin, Illinois, Iowa, and as far south as northern Missouri.
[11] One tornado touched down at Tama, along with numerous hail and high wind reports in the eastern part of the state.
Like the system in Ontario but unlike the squall line of the upper Midwest, this was a continuous series of storms that produced widespread damage along its path.
Some of the most spectacular footage came out of Providence harbor in Rhode Island, where a tanker caught in the winds exploded in the harbour while unloading gasoline.
The outage took place just after PECO had set record highs for electricity usage as a result of the extreme heat wave.
For the third consecutive day, a major derecho took place, albeit further southwest this time, making a direct hit on the St. Louis metropolitan area at about close to 7 p.m. on July 19.
These storms downed many trees atop active power lines, creating the largest electricity outage in the history of the City of St. Louis.
More than 1,200,000 residents of the area were left without power amidst a heat wave during an already hot and humid midwestern United States summer.
[23] The storms went on to hit other cities in Illinois, including Alton, O'Fallon, Edwardsville, Bethalto, Glen Carbon and East St. Louis.
The neighbouring towns of East Alton, Wood River, and Roxana house the third largest oil refinery in the United States.
Many people seeking generators or ice after the storms were faced with long queues at local grocery, hardware stores and gas stations.
The storms left a heightened awareness within local and state governments that this is one of the largest metropolitan areas in the country inside the outer belt of "Tornado Alley"; hence it is not completely safe.
The line rocked through the Quad Cities of Illinois and Iowa with 50-60 mph winds knocking out power to 127,000 before making another southerly turn.
[24] Barely 36 hours after being hit very hard by the July 19 storms, another derecho — albeit still developing at the time — slammed into the St. Louis area late that morning.
Missouri Governor Matt Blunt declared St Louis a State of Emergency and sent the National Guard to assist the citizens with shelter, food, supplies, etc.
The derecho that crossed into Ontario and Quebec was the result of a warm and very humid airmass that had plagued much of Central and Eastern Canada and the vast majority of the continental U.S.