EF1 tornado, St Clair to Otisco, Minnesota, August 5, 2024

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mphthis tornado

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mph

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

EF1

Date

August 5, 2024

Touchdown

6:19 PM CDT (23:19 UTC)

Lifted

6:33 PM CDT (23:33 UTC)

On the ground

14 minutes

Path length

6.1 miles (9.8 km)

Path width

150 yards (137 m)

Deaths

0

Injuries

0

Counties

Waseca and Blue Earth counties

Touchdown point

44.128, -93.813

Lift-off point

44.078, -93.717

Record number

2408051719-01

9 damage points were recorded along this path by NWS MPX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 105 mph.

• Multiple large trees down, large steel cover thrown over vehicle
• Mainly tree damage, large trees that were snapped were partially rotted
• A couple power poles down, large trees snapped
• Crops/tall grasses flattened, convergent

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

A nearly stationary front was draped across southern Minnesota on the afternoon of Monday, August 5, 2024. A very unstable airmass with strong shear was present along and south of the front. Two supercells developed over Nicollet and Watonwan Counties, then strengthened while tracking southeast. Supercells eventually formed a line of severe thunderstorms, which continued to result in occasional tornadoes and damaging wind gusts across south central MN.

The tornado touched down in northeastern Blue Earth County and moved east-southeast before tracking into Waseca County. While in Blue Earth County, it hit a couple sheds and also uprooted or broke several dozen trees. Several power poles were knocked down.

After moving east-southeast in Blue Earth County, the tornado entered Waseca County and turned to the southeast. It mostly moved across fields but it did break or uproot dozens of trees. It flipped a tractor on its side. Toward the end of its path, the tornado blew in a garage door of an old barn.

The tornado mostly moved across fields, but it did snap the trunks of multiple trees. Other trees were uprooted, with one falling on a power line.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

26 minutes of warning. NWS MPX issued a tornado warning for this county at 22:53 UTC, 26 minutes before the tornado touched down, in force until 23:30 UTC.

The county was under a tornado watch, issued at 22:25 UTC and running to 00:23 UTC.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:55 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

The Minneapolis radar (KMPX), 84 km away, was scanning. The volume nearest the touchdown began at 23:17 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2024 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

20 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.