On July 19 and 20, 2018, an unexpected strong tornado outbreak affected Iowa and nearby areas.

The event was triggered mostly by three supercells that produced several tornadoes across southeastern Iowa east and southeast of Des Moines.

At 21:00 UTC on July 19 (4 pm CDT), a large Storm-Relative Helicity (SRH) and low level wind shear was reported across the region.

Fueled by an interaction with an outflow boundary from the southern supercell, the storm produced a large, wedge EF3 tornado that directly struck the town of Marshalltown.

As the system trekked eastwards into July 20, damaging winds and hail became the main threat, with a 30% chance of strong wind across much of Arkansas, Tennessee and Kentucky, and a 45% chance of damaging hail across central Tennessee and Kentucky.

As part of the storm system as a whole, a duck boat tour sank in Table Rock Lake, Missouri, at approximately 7 pm CDT.

[43] Following these tornadoes, several counties in Iowa were declared disaster zones by Kim Reynolds.