The Ohio Valley was affected by one of the largest tornado outbreaks ever during the Memorial Day weekend on May 29–30.

However, the 2003 outbreak sequence produced several more destructive and violent tornadoes and had a much higher death toll than in May 2004.

On that day, a warm, moist airmass was sitting over Nebraska while an upper-level low developed in Colorado, with an attending dryline forming ahead of the advancing cold front.

By the time it entered Lancaster County, it measured an F4 on the Fujita scale and the damage path was 2.5 miles (4.0 km) wide.

Tornadoes on the 29th were focused from the Dakotas to Missouri and Oklahoma before shifting east to the Mississippi, Ohio and Tennessee Valleys on the 30th.

The official Storm Data archives from NOAA list a total of 168 tornadoes during the two-day period.

3 of the fatalities were caused by an F4 tornado that struck the Weatherby area in DeKalb County, Missouri late during the evening of May 29.

The tornado missed the Indianapolis Motor Speedway by six miles and forced post-racing events to be held indoors.

The tornado did however cause extensive damage across southern and eastern Marion County south of the downtown area.

[5] On this day, several clusters of thunderstorms traveled from the Midwest to the Mid-Atlantic States producing widespread damaging wind and weaker tornadoes across Michigan.

An F3 tornado tore through a residential subdivision just north of Lexington, Kentucky causing major damage to about 50 homes.