Tornadoes · United States · Illinois · 1958

F2 tornado, Lee, DeKalb, Kendall and Will counties, Illinois, August 15, 1958

This F2 tornado ran 74.5 miles across Lee, DeKalb, Kendall and Will counties on August 15, 1958, touching down at 3:00 AM GMT-5 and reaching 100 yards wide. It killed nobody, and did $50,000 to $500,000 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.

  1. F040 to 72 mph

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

  2. F173 to 112 mph

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

  3. F2113 to 157 mphthis tornado

    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. 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.

  5. F4207 to 260 mph

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

  6. 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.

  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.

The record

Rating
F2
Date
August 15, 1958
Touchdown
3:00 AM GMT-5 (08:00 UTC)
Path length
74.5 miles (119.9 km)
Path width
100 yards (91 m)
Deaths
0
Injuries
0
Property damage
$50,000 to $500,000
Counties
Lee, DeKalb, Kendall and Will counties
Touchdown point
41.770, -89.470
Lift-off point
41.500, -88.070
Record number
469

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

8.0 hours before the tornado, 128 km from the path. August 15, 1958.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 00:00Z on 1958-08-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 3554 joules per kilogram, CIN -3, lifted condensation level 1191 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Peoria Regional, IL at 00:00Z on 1958-08-15The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 111 square meters per square second, 0 to 6 km bulk shear 38 knots.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
3554 J/kg
Mixed-layer CIN
-3 J/kg
Surface CAPE
4088 J/kg
Mixed-layer LCL
1191 m above ground
0-6 km bulk shear
38 kt
0-1 km bulk shear
14 kt
0-1 km storm-relative helicity
111 m²/s²
0-3 km storm-relative helicity
115 m²/s²
Significant tornado parameter
1.5
Supercell composite
9.1
0-3 km lapse rate
7.2 K/km

Open this sounding in Storm Lab

Peoria Regional, IL (KPIA), 12:00Z

4.0 hours after it, 128 km from the path. August 15, 1958.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 12:00Z on 1958-08-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 98 joules per kilogram, CIN -151, lifted condensation level 1147 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Peoria Regional, IL at 12:00Z on 1958-08-15The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity -276 square meters per square second, 0 to 6 km bulk shear 48 knots.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
98 J/kg
Mixed-layer CIN
-151 J/kg
Surface CAPE
77 J/kg
Mixed-layer LCL
1147 m above ground
0-6 km bulk shear
48 kt
0-1 km bulk shear
49 kt
0-1 km storm-relative helicity
-276 m²/s²
0-3 km storm-relative helicity
-261 m²/s²
Significant tornado parameter
0.0
Supercell composite
-1.1
0-3 km lapse rate
5.3 K/km

Open this sounding in Storm Lab

This ground now

The live radar over the trackEvery 1958 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of August 15, 1958

4 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 156:00 AM GMT-5F1Vermilion, IL13.930$500 to $5,000
August 1512:20 PM GMT-4F2Aroostook, ME17.033$5,000 to $50,000
August 151:50 PM GMT-4F1Western Connecticut Planning Region, CT0.267$500 to $5,000
August 155:50 PM GMT-5F1Bosque, TX0.550$500 to $5,000

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.