TL;DR

Four tornadoes touched down across Iowa and Illinois on August 12, 2026, as a powerful line of severe thunderstorms swept through the Midwest. The strongest—a high-end EF1 with 110 mph winds—struck near Greeley, Iowa, causing significant damage to farmsteads. The outbreak also produced over 750 wind reports and 123 hail reports, including baseball-sized hail in northern Indiana.

A volatile morning across the Midwest delivered four confirmed tornadoes, widespread damaging winds, and large hail as a cluster of severe thunderstorms tracked from eastern Iowa into Illinois. The event unfolded during the morning and early afternoon hours of August 12, driven by extreme atmospheric instability and strong low-level wind shear.

## What happened in Iowa

Three tornadoes touched down in eastern Iowa between 1231 and 1245 UTC (7:31–7:45 a.m. CDT), all rated EF1 by the National Weather Service office in Davenport.

The most significant tornado began 5 miles west of Greeley, where it reached high-end EF1 intensity with peak winds of 110 mph. According to the NWS, the tornado "caused significant damage to two farmsteads at the beginning of its 2.4 mile long path," destroying two farm outbuildings.

Minutes later, a second EF1 tornado with maximum winds of 90 mph touched down 2 miles south-southeast of Greeley, damaging trees and crops across a 1.5-mile path. A hoop outbuilding was thrown into the south side of a farm structure.

A third EF1 tornado struck 4 miles north of Earlville at 1245 UTC, producing 95 mph winds. The NWS reported damage to trees, a house, and several farm outbuildings. "A tree fell on a house heavily damaging a garage," the local storm report noted.

## Illinois tornado near Seymour

A fourth tornado was confirmed at 2029 UTC (3:29 p.m. CDT) 3 miles south of Seymour, Illinois, by the NWS office in Lincoln. Details on the damage path and rating were not immediately available in preliminary storm reports.

## Widespread wind damage and giant hail

Beyond the tornadoes, the severe weather outbreak was defined by prolific wind and hail reports.

The NWS received 750 wind reports in the 24-hour period ending midday August 12. Damaging winds began early in the morning across Iowa, with a 75 mph gust reported near Independence at 1207 UTC. The Independence Municipal Airport recorded a 60 mph gust minutes later. Observers near Edgewood, Iowa, reported 70 mph winds at 1238 UTC.

As the storms pushed into Illinois and Indiana, wind damage intensified. Trees, power lines, and structures were damaged across a broad swath of the Midwest, with impacts extending into Ohio, West Virginia, and the Carolinas.

123 hail reports were logged, with the most impressive stones falling in northern Indiana. Baseball-sized hail (2.75 inches) was confirmed 3 miles east of English Lake, Indiana, at 1430 UTC, causing damage to vehicles on Toto Road. A photo posted to social media showed what appeared to be a 3-inch hailstone near Toto, though no official measurement was available. Hen egg to tennis ball-sized hail (2.5 inches) was documented in Knox, Indiana, also causing vehicle damage.

Other notable hail reports included 2.5-inch stones near Johnson Siding, South Dakota, and half-dollar-sized hail in North Carolina during the afternoon.

## The atmospheric setup

The Storm Prediction Center's Day 1 Convective Outlook highlighted the volatile environment in place across the Midwest. A 12 UTC sounding from Davenport, Iowa, measured 4,300 J/kg of mixed-layer CAPE—an extraordinary level of atmospheric instability for a morning environment.

SPC noted that the airmass was "very moist and extremely unstable." Dewpoints in the 70s combined with steep mid-level lapse rates created a classic severe weather environment. Effective bulk shear values of 35+ knots supported organized storm structures capable of producing tornadoes, large hail, and damaging straight-line winds.

## Context: August tornadoes in the Midwest

While tornadoes are less common in August than during the spring peak, they are far from rare across the Midwest. Warm-season severe weather events are often driven by morning convective complexes and mesoscale boundaries left behind by overnight storms—exactly the pattern observed on August 12.

The four tornadoes reported on August 12 bring the recent total to seven confirmed tornadoes across the central United States in just three days, following three landspout tornadoes on August 10 across the Plains.

Iowa and Illinois have both experienced significant tornado events in August historically. The atmospheric ingredients—high CAPE, strong low-level shear, and ample moisture—remain in place during the late summer months, particularly when upper-level troughs interact with lingering heat and humidity.

## Ongoing severe weather threat

As of midday August 12, multiple severe thunderstorm watches remained in effect across Iowa, Illinois, and Indiana, with expiration times extending into the early afternoon. SPC's Day 1 outlook maintained a Slight Risk across portions of the Midwest, with continued threats of damaging winds and large hail through the evening hours.

The Day 2 outlook (valid August 13) indicated a Marginal Risk across parts of the Ohio Valley and Midwest, suggesting the potential for additional isolated severe storms.

## Lessons from a morning outbreak

The August 12 event underscores the importance of monitoring severe weather during non-traditional hours. All three Iowa tornadoes occurred before 8 a.m. local time, when many residents were beginning their morning routines. Nighttime and early-morning tornadoes are statistically more deadly than afternoon events, in part because people are asleep or less situationally aware.

Wireless Emergency Alerts (WEA) for tornado warnings are designed to break through Do Not Disturb mode on most smartphones, providing a critical layer of alerting during overnight and early-morning hours. Third-party weather apps are silenced by Do Not Disturb, though Wireless Emergency Alerts for tornado warnings still break through on most phones.

For those in tornado-prone regions, having multiple methods of receiving warnings—including NOAA Weather Radio, smartphone alerts, and outdoor sirens—remains the best practice.

VORTEX is a free web app at vortexintel.app that monitors severe weather nationwide. Pro ($4.99/month) places phone calls to your phone when a tornado or flash flood warning is issued for a location you care about — calls can ring through Do Not Disturb once you enable Emergency Bypass for the number, unlike most third-party app notifications.