Winds of 80-100 miles per hour were reported during a 10-hour June 29 storm event called a derecho. The storm left more than 4 million utility customers without power across 11 states and the District of Columbia. Many areas were without power for about a week.
An U.S. Energy Department report on the storm, a straight-line wind event that rolled across the country, said more consumers were affected by the storm than from Hurricane Irene, a category 3 hurricane that hit the eastern U.S. coast in August of last year. That hurricane, one of the costliest in terms of damage, left 3.2 million consumers without power.
The Energy Department, in a 17-page report on the derecho, said power restoration was complicated by the large coverage area of the storm and minimal warning time.
The report said moderate winds were expected mid-afternoon on the day of the storm but had increased to severe warnings for an area stretching from Ohio to West Virginia by later that day.
"Analysis of forecasting prior to the 2012 derecho indicates that there was minimal notice to any of the utilities in impacted areas that a storm of the 2012 derecho's magnitude was likely," the report read.