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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />the county. <br />4.3.3.2. Range of magnitude <br />Maximum wind speeds: <br />• Hennepin: <br />20, 1951 <br />1980 <br />o Measured 100 mph, Wold-Chamberlain Field (MSP), July <br />o Measured 86 mph at Flying Cloud Airport, on 15 July <br />o Estimated over 100 mph on July 3, 1983 <br />• Other Twin Cities Metro: <br />• Minnesota: <br />• Region: <br />0 110 mph sustained, gust 180 mph, St. Paul, Aug 20, 1904 <br />0 121 mph, Donaldson, MN, September 1, 2011 <br />0 117 mph, Alexandria, July 19, 1983 <br />0 128 mph (Northeast of Madison, WI May 31, 1998) <br />0 126 mph, Atkins, IA, August 10, 2020 (140 mph estimated <br />from damage surveys) <br />Maximum width: 100 miles (Kansas —The "Super Derecho of May 8, 2009) <br />Longest track: 1300 miles (The Boundary Waters -Canadian Derecho July 4-5, 1999) <br />Longest duration: 22 hours (The Boundary Waters -Canadian Derecho July 4-5, 1999) <br />Costliest US Derecho: $7.5 Billion (The Iowa -Midwest Derecho of August 10, 2020) <br />Deadliest US Derecho: 73 killed (The "More Trees Down" Derecho July 4-5, 1980) <br />4.3.3.3. Spectrum of Consequences B211b <br />Extreme thunderstorm winds and derechos are most common in the warm season and pose risks to those <br />involved in outdoor activities. Campers or hikers in forested areas are vulnerable to being injured or killed <br />by falling trees. Boaters risk injury or drowning from storm winds and high waves that can overturn boats. <br />Trees around lakes pose risks to walkers, joggers, and cyclists. At outside events such as fairs and festivals, <br />people may be killed or injured by collapsing tents and flying debris. Additionally, anyone caught outside <br />may be injured by flying debris. Any person without adequate shelter is at significant risk in extreme <br />thunderstorm winds. <br />Occupants of cars and trucks also are vulnerable to being hit by falling trees and utility poles. Further, high <br />profile vehicles such as semi -trailer trucks, buses, and sport utility vehicles may be blown over. <br />Even those indoors may be at risk for death or injury during derechos. Mobile homes may be overturned <br />or destroyed, while barns and similar buildings can collapse. People inside homes, businesses, and schools <br />are sometimes victims of falling trees and branches that crash through walls and roofs; they also may be <br />injured by flying glass from broken windows. Finally, structural damage to the building itself (for example, <br />removal of a roof) could pose danger to those within. <br />Throughout Hennepin County, and especially in suburban and urban areas, electrical lines are vulnerable <br />to high winds and falling trees. In addition to posing a direct hazard to anyone caught below the falling <br />lines, wind damage to the power infrastructure can result in massive, long-lasting power outages. <br />82 <br />