High Quality Content by WIKIPEDIA articles! The Western Wisconsin Derecho was a derecho, or severe weather system, that occurred through several counties of Western Wisconsin on July 15, 1980. It caused nearly $160M in damage (1980 dollars) and one person was killed. At the time, it was the worst natural disaster in Wisconsin history. To this day, the storm is still referred to as "The July 15th (1980) Storm," "July 15th, 1980," or simply "The Storm."