Tornadoes · United States · Illinois · 1959

F1 tornado, Cook County, Illinois, May 26, 1959

This F1 tornado ran 0.1 miles across Cook County on May 26, 1959, touching down at 8:34 PM GMT-5 and reaching 10 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.

  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 mphthis tornado

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

  3. 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.

  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
F1, estimated from the damage record rather than surveyed
Date
May 26, 1959
Touchdown
8:34 PM GMT-5 (01:34 UTC)
Path length
0.1 miles (0.2 km)
Path width
10 yards (9 m)
Deaths
0
Injuries
0
Property damage
$50 to $500
County
Cook County
Touchdown point
42.000, -87.970
Record number
295

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

1.6 hours before the tornado, 201 km from the path. May 27, 1959.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 00:00Z on 1959-05-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 87 joules per kilogram, CIN -158, lifted condensation level 1358 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 00:00Z on 1959-05-27The 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 33 square meters per square second, 0 to 6 km bulk shear 19 knots.193958Sfc1 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
87 J/kg
Mixed-layer CIN
-158 J/kg
Surface CAPE
182 J/kg
Mixed-layer LCL
1358 m above ground
0-6 km bulk shear
19 kt
0-1 km bulk shear
10 kt
0-1 km storm-relative helicity
33 m²/s²
0-3 km storm-relative helicity
93 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
7.1 K/km

Open this sounding in Storm Lab

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

10.4 hours after it, 201 km from the path. May 27, 1959.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 12:00Z on 1959-05-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 240 joules per kilogram, CIN -98, lifted condensation level 944 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 1959-05-27The 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 131 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
240 J/kg
Mixed-layer CIN
-98 J/kg
Surface CAPE
34 J/kg
Mixed-layer LCL
944 m above ground
0-6 km bulk shear
38 kt
0-1 km bulk shear
29 kt
0-1 km storm-relative helicity
131 m²/s²
0-3 km storm-relative helicity
140 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.9 K/km

Open this sounding in Storm Lab

The surface observations

Chicago OHare (ORD), 5 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
00:00 UTC8068160° 16 kt1011.5
01:00 UTC7966160° 22 kt1011.5
02:00 UTC6968250° 12 kt1011.9-TSRA
03:00 UTC7265180° 15 kt1012.5-SHRA

From the Iowa Environmental Mesonet's archive of airport observations.

This ground now

The live radar over the trackEvery 1959 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of May 26, 1959

14 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 269:00 AM GMT-5F2Fremont, IA15.9400$5,000 to $50,000
May 261:25 PM GMT-5F1Iroquois, IL0.110$50 to $500
May 264:15 PM GMT-5F0Cedar, NE0.110$50 to $500
May 264:45 PM GMT-5F3Trempealeau, WI34.3672$50,000 to $500,000
May 264:45 PM GMT-5F2Rusk, WI2.233$5,000 to $50,000
May 265:15 PM GMT-5F1Miami, IN0.110$500 to $5,000
May 266:30 PM GMT-5F0Cuming, NE0.110$50 to $500
May 268:00 PM GMT-5F0Rice, KS0.110
May 268:00 PM GMT-5F0Rice, KS0.110
May 268:00 PM GMT-5F0Rice, KS0.110
May 268:18 PM GMT-5F3Carter, OK3.3608$5,000 to $50,000
May 268:25 PM GMT-5F0Rice, KS0.110
May 269:10 PM GMT-5F1Jefferson, OK2.0100$5,000 to $50,000
May 2611:30 PM GMT-5F1Hughes, OK0.110

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.