The heat wave of 2006 derecho series were a set of derechos — severe winds with powerful thunderstorms — that occurred on July 17–21, 2006. The first storms hit a wide swath of north-central and northeastern North America that stretched from the Upper Midwest through much of Ontario and into the northeastern United States. Another round struck the middle Mississippi River Valley, including two derechos that hit St. Louis, Missouri. The storms left more than three million people without power, some more than once and some for weeks.
Northeastern Ontario derecho (July 17, 2006)
Northern Michigan and Northeastern Ontario
The derecho originated from a severe thunderstorm that was forming across portions of the Upper Peninsula and the northernmost parts of the lower Peninsula of Michigan in the early afternoon hours of July 17. It crossed the North Channel into Northeastern Ontario near Sault Ste. Marie, where it quickly developed into a derecho line. As it crossed Manitoulin Island just southeast of Sault Ste. Marie in Lake Huron, numerous trees were uprooted and some homes sustained heavy damage. An official wind gust of 128 km/h (80 mph) was recorded at the Killarney weather station on the north shore of Lake Huron. Tornado warnings were issued for the area, but damage was consistent with severe straight-line winds.
At about 15:30-16:00 EDT (19:30-20:00 UTC), the storm raced through Sudbury, toppling hydro poles and trees. Highway 69, the major highway linking Sudbury and Toronto, had to be shut down because electrical wires blocked the highway. At that point, the storm system started to take the form of a comma, signature of a fast-moving progressive derecho.
At about 17:30 EDT (21:30 UTC), the storm gathered further intensity before striking North Bay, a city of over 50,000, and the surrounding Nipissing District. Numerous trees were uprooted or snapped off and many buildings sustained heavy surface and some structural damage. Just south of the city, radio towers and a lighthouse were demolished by the violent winds. 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). Tornado warnings were in effect for the area and several funnels were reported but none has been confirmed. 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. The town of Mattawa and rural areas in West Nipissing were particularly hard hit as storage siloes were torn apart, roofs were torn from buildings, utility poles were snapped in two and roads were entirely impassable from the debris strewn across them, in some cases for weeks after the storm.
At the same time, the storm affected the Algonquin Park region (mostly the northern portion) and fallen trees killed at least one man from Michigan and injured another, also from Michigan, who were on a canoe trip near Kiosk, a small community located at the northern end of the park.
Ottawa Valley, Eastern Ontario and Southwestern Quebec
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. There were numerous reports of damage, particularly blown-off or damaged roofs.