fatalities occurred in an apartment building that collapsed. Damage was estimated at $18 million. The population of the town diminished soon after to less than half of what it was previous to the tornado, from 315 to 145 in April 1999. May 30–31 Southern Great Lakes derecho This derecho got its start from a developing low pressure system that moved into the northern Great Plains and Great Lakes. The derecho formed from the same storm system that spawned the Spencer, South Dakota Tornado, which killed six people. The supercell thunderstorm which produced that tornado transitioned into the derecho which killed another six people. It would become the most destructive natural disaster to hit the Upper Midwest in recent memory. Minnesota The most damage in Minnesota occurred at the northern edge in Sibley and McLeod Counties. Winds ranged from in those two counties. After the derecho raced through Minnesota, tens of thousands of trees were blown down. There were 500,000 customers without power. Over 100 homes were destroyed or damaged beyond repair. Twenty-two people were injured. The derecho caused $50 million in damage in southern Minnesota and northern Wisconsin. Wisconsin The derecho raced across Wisconsin in only three hours killing one person in Washington County when a tree fell through the roof and onto her bed where she was sleeping. It injured 37 people in Wisconsin. Many utility companies and emergency customers said that this was the most damaging straight-line wind thunderstorm event in 100 years. Five thousand homes and businesses were damaged and 24 were destroyed. An area of south-central, south-east, and east-central Wisconsin reported wind gusts of over from this thunderstorm complex with an all-time official state record gust of north-east of Watertown in Dodge County. As with other derechos like the July 4, 1977 blow-down in northern Wisconsin, there were other unofficial reports of higher winds as well as estimates of such, including winds of sustained for a number of minutes and gusts up to also in Dodge County and/or adjacent sections of Fond du Lac County. The roar of the wind from the derecho was audible up to away as the storm traversed this region. Road signs and other metal structures were found thrown about and even violently twisted in the area of 100 mph-plus wind from north-east Dane County through Dodge and Fond du Lac and Washington counties—evidence of both straight-line winds and rotor downbursts were