Tornadoes · United States · Illinois · 1968
F1 tornado, Warren and Knox counties, Illinois, July 17, 1968
This F1 tornado ran 3.8 miles across Warren and Knox counties on July 17, 1968, touching down at 7:30 PM GMT-5 and reaching 127 yards wide. It killed nobody, and did $50 to $500 of property damage.
The rating scale
Tracks are drawn in the color of the rating. The Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
F040 to 72 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mphthis tornado
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
F2113 to 157 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.
F3158 to 206 mph
Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.
F4207 to 260 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
F5261 to 318 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.
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.
The record
- Rating
- F1
- Date
- July 17, 1968
- Touchdown
- 7:30 PM GMT-5 (00:30 UTC)
- Path length
- 3.8 miles (6.1 km)
- Path width
- 127 yards (116 m)
- Deaths
- 0
- Injuries
- 0
- Property damage
- $50 to $500
- Counties
- Warren and Knox counties
- Touchdown point
- 40.930, -90.520
- Lift-off point
- 40.930, -90.430
- Record number
- 454
The air that afternoon
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.
Peoria Regional, IL (KPIA), 00:00Z
0.5 hours before the tornado, 79 km from the path. July 18, 1968.
- Mixed-layer CAPE
- 358 J/kg
- Mixed-layer CIN
- -31 J/kg
- Surface CAPE
- 1811 J/kg
- Mixed-layer LCL
- 1275 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km bulk shear
- 10 kt
- 0-1 km storm-relative helicity
- 53 m²/s²
- 0-3 km storm-relative helicity
- 191 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.0
- 0-3 km lapse rate
- 6.5 K/km
Peoria Regional, IL (KPIA), 12:00Z
11.5 hours after it, 79 km from the path. July 18, 1968.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -4293 J/kg
- Surface CAPE
- 117 J/kg
- Mixed-layer LCL
- 542 m above ground
- 0-6 km bulk shear
- 6 kt
- 0-1 km bulk shear
- 12 kt
- 0-1 km storm-relative helicity
- 53 m²/s²
- 0-3 km storm-relative helicity
- 69 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 4.7 K/km
The surface observations
Burlington (BRL), 57 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 23:00 UTC | 81 | 71 | 110° 6 kt | SHRA | ||
| 00:00 UTC | 81 | 71 | 240° 8 kt | |||
| 01:00 UTC | 79 | 71 | 190° 8 kt | |||
| 02:00 UTC | 77 | 71 | 230° 6 kt |
From the Iowa Environmental Mesonet's archive of airport observations.
This ground now
The live radar over the trackEvery 1968 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are
The other tornadoes of July 17, 1968
10 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| July 17 | 1:47 PM GMT-5 | F0 | Stearns, MN | 0.1 | 10 | |||
| July 17 | 3:55 PM GMT-4 | F2 | Hillsborough, NH | 0.1 | 17 | $5,000 to $50,000 | ||
| July 17 | 6:30 PM GMT-4 | F1 | Worcester, MA | 0.3 | 17 | $500 to $5,000 | ||
| July 17 | 6:30 PM GMT-5 | F0 | Carson, TX | 0.5 | 100 | |||
| July 17 | 6:55 PM GMT-5 | F0 | Callaway, MO | 0.5 | 50 | $500 to $5,000 | ||
| July 17 | 7:15 PM GMT-5 | F1 | Comanche, KS | 0.5 | 300 | |||
| July 17 | 7:15 PM GMT-5 | F1 | Comanche, KS | 0.1 | 10 | |||
| July 17 | 9:02 PM GMT-5 | F0 | Carson, TX | 4.5 | 33 | |||
| July 17 | 9:02 PM GMT-5 | F0 | Gray, TX | 3.8 | 33 | |||
| July 17 | 9:35 PM GMT-5 | F0 | Wheeler, TX | 0.1 | 10 |
What this means
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.
Sources
NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.