High Quality Content by WIKIPEDIA articles! The heat wave of 2006 derecho series was a series of severe wind events associated with powerful thunderstorms, known as derechos, that occurred in a five-day period between July 17 and July 21, 2006. The first storms took place across a wide swath of north-central and northeastern North America stretching from the Upper Midwest, through much of Ontario and into the northeastern United States. Another round of storms affected the middle Mississippi River Valley, notably the city of St. Louis, Missouri, which took a direct hit twice by powerful derechos. During the period, over 3,000,000 people across the region were left without power from the storms, some more than once and some did not have power restored for weeks after the event.