The Union of Concerned Scientists said MISO’s most devastating power outages in the past decade can be attributed to an increasingly unstable climate and compounding weather events.
UCS published a new analysis naming climate change as the culprit behind the 10 most severe blackouts in the footprint since 2014. The nonprofit science advocacy organization said all of the 10 largest power outage events over the decade have occurred since 2020, with half occurring in 2020 itself. UCS said each incident in the top 10 lasted multiple days and was associated with “compound weather events occurring over a large geographic region.”
UCS defined the worst power outages as the “greatest number of customers without power on a single day.” Outages varied from 800,000 to 1.6 million customers without power across the MISO footprint.
UCS said MISO and its membership should be girding the grid to withstand extreme weather and warned that a lack of preparedness will spell more outages for more customers.
Across MISO, top spots were claimed by derechos across the Midwest: two in 2020 and one in 2021. On June 11, 2020, the remnants of Tropical Storm Cristobal joined with a low-pressure system over the Great Lakes to produce maximum 75 mph wind gusts and several tornadoes. Two months later, another derecho that wrought $11 billion in damage cut power to parts of South Dakota, Nebraska, Iowa, Illinois, Wisconsin, Indiana, Michigan and Ohio. This time, winds reached 100 mph, and the storm spawned 26 weak tornadoes.
Days later, MISO’s Gulf of Mexico weathered Hurricane Laura on Aug. 27, 2020, which made landfall as a Category 4 in coastal Louisiana. Extensive flooding and wind damage in coastal Louisiana and Texas accounted for much of the hurricane’s $19 billion in damage.
Weeks later, Hurricanes Delta and Zeta followed on Oct. 10, 2020, and Oct. 29, 2020, respectively. The two followed an almost identical point of entry in Louisiana. Delta spawned far-flung tornadoes and brought more flooding to already inundated drainage systems in eastern Texas, southern and central Louisiana, and portions of Mississippi and Arkansas. It caused $2.9 billion in damage. Zeta’s higher winds caused $3.9 billion in damage to the grid.
“In the 10 worst outage events reviewed, it is never merely a severe thunderstorm or a hurricane alone that leads to these extensive outages. Rather, it is a derecho with multiple tornadoes and wildfires. Or it is a hurricane with tornadoes, coastal and inland flooding, follow-on fires, and extreme heat or damaged industrial facilities causing the accidental release of toxins,” UCS wrote in the new analysis.
The group noted that nearly all the most acute outages were linked to high winds, though floods, fire and ice also damaged the system.
“Where high winds dominate, damage to the grid results either from trees falling on power and transmission lines or from winds directly bringing down poles and lines,” UCS wrote. The nonprofit said repair and replacement of wind-damaged lines “may be among the biggest factors driving recent increases in electricity prices,” a little-reported detail.
“Sequential storms like back-to-back Hurricanes Laura, Delta and Zeta in 2020 pose another type of challenge, leaving hardly any time for communities to recover between events,” UCS wrote. “As grid-damaging storms occur more frequently, areas that have experienced damages have little time to rebuild before the next extreme event and therefore are more vulnerable to deeper losses. … This means that people’s homes have been covered only by tarps, not solid, new roofs; water-damaged structures have not yet dried out; and dunes have not re-formed, allowing coastal surges to reach deeper inland.”
UCS said the repeated bouts of severe weather mean poles and power lines have barely been stood back up or restrung when they’re vulnerable to severe weather again.
In early August 2021, another derecho targeted the MISO footprint, this time bringing hurricane-force winds and flash flooding to a nearly 800-mile stretch from southeastern South Dakota and northeastern Nebraska through Iowa and on to northern Illinois, southern Wisconsin, northern Indiana, southern Michigan and western Ohio. The long line of thunderstorms caused an estimated $11.5 billion in destruction.
By the end of August 2021, Hurricane Ida — another Category 4 — followed a familiar path up Louisiana, generated at least 35 tornadoes and caused $75 billion in damage ($55 billion in Louisiana alone). Individual power outages lasted for more than a month in some cases, and some of the nearly 90 deaths attributable to the storm were due to a lack of air conditioning.
To round out 2021, on Dec. 16, uncharacteristic thunderstorms targeted Minnesota, Iowa and Nebraska with high winds. Minnesota reportedly logged its first-ever tornado in December.
UCS completed its list with severe thunderstorms that formed across southern Michigan in late August 2022 and a punishing, dayslong winter storm in late February 2023 that delivered ice, wind and heavy snow across several states.
“Extreme weather events can no longer be shrugged away as acts of God or system anomalies that we have no power to foresee or plan for,” report lead author Rachel Licker said in a press release. “Many parts of the central United States are projected to experience increases in severe thunderstorms, including derechos and hailstorms, and greater rainfall from hurricanes that make landfall. Some parts of the region may see more intense snowstorms, as well. Policymakers need to increase the electricity grid’s resilience to worsening climate change-fueled extreme weather or people will lose electricity, heat and air conditioning when they need it most. Failure to act is negligence that some could pay for with their lives.”
Report co-author Susanne Moser said it’s clear extreme storms supercharged by a warming climate are driving serious outages.
“As grid-damaging storms occur more frequently, areas directly affected have little time to rebuild before the next extreme weather event and end up spiraling into deeper and deeper vulnerability. Understanding the risks this poses for the electricity grid — and investing in the grid to mitigate those risks — is a question of safety for people and their families,” Moser said.

