The Upper Great Lakes severe weather outbreak of August 23, 1998 was a severe weather outbreak that affected parts of Wisconsin, and the Upper Peninsula of Michigan. The outbreak occurred on August 23, 1998, and caused millions of dollars in damage to the region. One fatality is attributed to this severe weather event, when a severe thunderstorm knocked a tree onto a camper killing its sole occupant. A supercell spawned a F3 tornado that ripped across Door County causing $6.5 million in damages. It was the 8th most costly tornado in Wisconsin history injuring two people, destroying multiple structures and disrupting the regional economy and tourism. Two storms moved through the Fox Valley producing a minimal F0 tornado, but devastating amounts of hail. Damages from the hail were estimated to be around $5 million and damaged many structures and vehicles. Wisconsin Governor Tommy Thompson requested a Presidential Disaster Declaration from President Bill Clinton for the disaster, but was denied.

This page documents the tornadoes and tornado outbreaks of 1998, primarily in the United States. Most tornadoes form in the U.S., although some events may take place internationally. Tornado statistics for older years like this often appear significantly lower than modern years due to fewer reports or confirmed tornadoes, however by the 1990s tornado statistics were coming closer to the numbers we see today.