Tornadoes · United States · Illinois · 1965

F4 Crystal Lake tornado, Illinois, April 11, 1965

This F4 tornado ran 9.1 miles across McHenry and Lake counties on April 11, 1965, touching down at 3:20 PM GMT-6 and reaching 400 yards wide. It killed 6 people and injured 75.

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 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 mphthis tornado

    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
F4
Date
April 11, 1965
Touchdown
3:20 PM GMT-6 (21:20 UTC)
Path length
9.1 miles (14.6 km)
Path width
400 yards (366 m)
Deaths
6
Injuries
75
Counties
McHenry and Lake counties
Touchdown point
42.220, -88.380
Lift-off point
42.280, -88.180
Record number
136

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), 12:00Z

9.3 hours before the tornado, 207 km from the path. April 11, 1965.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 12:00Z on 1965-04-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 213 joules per kilogram, CIN -75, lifted condensation level 966 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 1965-04-11The 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 191 square meters per square second, 0 to 6 km bulk shear 59 knots.1939587897117136Sfc1 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
213 J/kg
Mixed-layer CIN
-75 J/kg
Surface CAPE
40 J/kg
Mixed-layer LCL
966 m above ground
0-6 km bulk shear
59 kt
0-1 km bulk shear
31 kt
0-1 km storm-relative helicity
191 m²/s²
0-3 km storm-relative helicity
120 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.5
0-3 km lapse rate
5.9 K/km

Open this sounding in Storm Lab

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

2.7 hours after it, 207 km from the path. April 12, 1965.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 00:00Z on 1965-04-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -13493, lifted condensation level 2633 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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 1965-04-12The 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 197 square meters per square second, 0 to 6 km bulk shear 94 knots.1939587897117136156Sfc1 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
0 J/kg
Mixed-layer CIN
-13493 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
2633 m above ground
0-6 km bulk shear
94 kt
0-1 km bulk shear
26 kt
0-1 km storm-relative helicity
197 m²/s²
0-3 km storm-relative helicity
82 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
7.6 K/km

Open this sounding in Storm Lab

This ground now

The live radar over the trackEvery 1965 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of April 11, 1965

44 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 113:30 AM GMT-6F2Muskogee, OK0.110$500 to $5,000
April 1112:55 PM GMT-6F4Cedar, IA91.520013$500,000 to $5 million
April 111:15 PM GMT-6F1Chickasaw, IA49.9300$50,000 to $500,000
April 112:00 PM GMT-6F1Green, WI27.116740$500,000 to $5 million
April 112:30 PM GMT-6F2Jefferson, WI14.51,320328$500,000 to $5 million
April 112:45 PM GMT-6F1Crawford, WI13.310$5,000 to $50,000
April 113:50 PM GMT-6F2Lake, IL4.5200$50,000 to $500,000
April 113:50 PM GMT-6F1Walworth, WI1.950$50,000 to $500,000
April 113:55 PM GMT-6F1Walworth, WI1.010$5,000 to $50,000
April 114:00 PM GMT-6F1Kane, IL0.3150$50,000 to $500,000
April 114:04 PM GMT-6F1Lake, IL0.5250$50,000 to $500,000
April 114:14 PM GMT-6F1Monroe, WI2.050$5,000 to $50,000
April 114:45 PM GMT-6F3Starke, IN35.62501082$5 million to $50 million
April 115:54 PM GMT-5F4Ottawa, MI20.63005142$500,000 to $5 million
April 115:10 PM GMT-6F3Porter, IN33.110$5 million to $50 million
April 116:15 PM GMT-5F4Dunlap tornado, IN21.21031252
April 116:40 PM GMT-5F4Midway tornado, IN21.6177541$50,000 to $500,000
April 116:00 PM GMT-6F4Hillsdale tornado, Indiana and Michigan90.31,76023294$50 million to $500 million
April 117:05 PM GMT-5F1Allegan, MI19.520019$50,000 to $500,000
April 117:07 PM GMT-5F4Tippecanoe, IN21.850044
April 117:10 PM GMT-5F4Twin Lakes tornado, IN37.033336321
April 117:20 PM GMT-5F4Russiaville–Kokomo–Marion tornado, IN48.088025835$50 million to $500 million
April 117:30 PM GMT-5F3Kalamazoo, MI14.215017$50,000 to $500,000
April 117:40 PM GMT-5F3Barry, MI14.1105$50,000 to $500,000
April 117:40 PM GMT-5F4Branch, MI80.51021293
April 117:50 PM GMT-5F4Lebanon–Sheridan tornado, IN45.71,66728123$5 million to $50 million
April 117:10 PM GMT-6F4Berne tornado, Indiana and Ohio52.5104125$5 million to $50 million
April 118:15 PM GMT-5F4Clinton, MI21.010018$50,000 to $500,000
April 118:25 PM GMT-5F2Montcalm, MI15.14401$50,000 to $500,000
April 118:30 PM GMT-5F2Gratiot, MI0.150$5,000 to $50,000
April 118:30 PM GMT-5F2Gratiot, MI0.550$5,000 to $50,000
April 118:30 PM GMT-5F2Gratiot, MI1.050$5,000 to $50,000
April 118:50 PM GMT-5F2Bay, MI9.9102$50,000 to $500,000
April 119:00 PM GMT-5F2Tuscola, MI9.010$50,000 to $500,000
April 118:30 PM GMT-6F4Toledo tornado, Ohio and Michigan5.620018236$5 million to $50 million
April 119:30 PM GMT-5F4Cairo tornado, OH32.540013104$500,000 to $5 million
April 1110:00 PM GMT-5F4Fort Loramie tornado, OH18.4300350$500,000 to $5 million
April 1110:15 PM GMT-5F3Seneca, OH15.0300430$50,000 to $500,000
April 1111:05 PM GMT-5F4Grafton–Strongsville tornado, OH22.040018200$5 million to $50 million
April 1111:15 PM GMT-5F1Preble, OH0.110$5,000 to $50,000
April 1111:30 PM GMT-5F1Medina, OH8.22006$50,000 to $500,000
April 1111:30 PM GMT-5F2Union, OH22.2400462$500,000 to $5 million
April 1111:50 PM GMT-5F1Greene, OH0.110$5,000 to $50,000
April 1112:30 AM GMT-5F1Pickaway, OH38.430013$50,000 to $500,000

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.