Tornadoes · United States · Illinois · 2020
Unrated tornado, Pequot, Illinois, May 17, 2020
This Unrated tornado ran 0.5 miles across Grundy County on May 17, 2020, touching down at 5:26 PM CDT and reaching 25 yards wide. It killed nobody.
The rating scale
Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
EF065 to 85 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
Unratedthis tornado
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
- Unrated
- Date
- May 17, 2020
- Touchdown
- 5:26 PM CDT (22:26 UTC)
- Lifted
- 5:27 PM CDT (22:27 UTC)
- On the ground
- 1 minutes
- Path length
- 0.5 miles (0.8 km)
- Path width
- 25 yards (23 m)
- Deaths
- 0
- Injuries
- 0
- County
- Grundy County
- Touchdown point
- 41.260, -88.280
- Lift-off point
- 41.260, -88.270
- Record number
- 2005171626-01
What the Weather Service recorded
Heavy rain fell across many areas of northeast Illinois on May 17th producing widespread flooding which continued into May 18th. Two brief tornadoes also occurred during the afternoon of May 17th. Scattered showers produced a few funnel clouds on May 18th. Some of the highest 48 hour rainfall totals ending Monday morning May 18th included 8.61 inches in River Forest; 5.18 inches near Oak Forest; 4.75 inches near Burr Ridge; 4.70 inches three miles southwest of Midway Airport; 4.59 inches in Palos Heights; 4.14 inches in Burr Ridge; 3.99 inches in Joliet; 3.88 inches in Harwood Heights; 3.80 inches at the National Weather Service office in Romeoville; 3.73 inches in Algonquin; 3.60 inches near Manhattan; 3.59 inches in Minooka; 3.59 inches at Chicago O'Hare Airport (ORD) and 3.32 inches in Cary.
A brief tornado touched down in eastern Grundy County. No damage was reported.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 09:00 UTC | 01:12 UTC | Flash Flood Watch | LOT |
| 19:14 UTC | 22:02 UTC | Flood Advisory | LOT |
| 20:29 UTC | 22:03 UTC | Flood Advisory | LOT |
| 21:32 UTC | 03:30 UTC | Flash Flood Warning | LOT |
| 02:34 UTC | 02:40 UTC | Flood Warning | LOT |
| 03:10 UTC | 09:00 UTC | Flood Warning | LOT |
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 forecast that day
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 19:54 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 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.
Lincoln, IL (KILX), 12:00Z
10.4 hours before the tornado, 126 km from the path. May 17, 2020.
- Mixed-layer CAPE
- 40 J/kg
- Mixed-layer CIN
- -26 J/kg
- Surface CAPE
- 62 J/kg
- Mixed-layer LCL
- 599 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 167 m²/s²
- 0-3 km storm-relative helicity
- 173 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 5.1 K/km
Lincoln, IL (KILX), 00:00Z
1.6 hours after it, 126 km from the path. May 18, 2020.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -82285 J/kg
- Surface CAPE
- 64 J/kg
- Mixed-layer LCL
- 1107 m above ground
- 0-6 km bulk shear
- 39 kt
- 0-1 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- -136 m²/s²
- 0-3 km storm-relative helicity
- 4 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 4.9 K/km
The surface observations
Morris-Washburn (C09), 22 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 20:35 UTC | 67.6 | 67 | 160° 17 kt | 21 | 1005.1 | |
| 20:55 UTC | 65 | 64.4 | 220° 7 kt | 1005.1 | +RA | |
| 21:15 UTC | 65 | 64.4 | 180° 5 kt | 1005.1 | RA | |
| 21:35 UTC | 65.3 | 64.6 | 160° 4 kt | 1004.7 | +RA | |
| 21:55 UTC | 64.8 | 64.4 | 0° 0 kt | 1004.4 | +RA | |
| 22:15 UTC | 64 | 63.5 | 290° 3 kt | 1004.7 | +VCTSRA | |
| 22:35 UTC | 64 | 63.5 | 290° 5 kt | 1005.1 | +VCTSRA | |
| 22:55 UTC | 63 | 62.8 | 340° 6 kt | 1004.4 | +VCTSRA | |
| 23:15 UTC | 62.8 | 62.4 | 290° 9 kt | 1005.1 | RA | |
| 23:35 UTC | 62 | 61.7 | 0° 0 kt | 1005.1 | RA | |
| 23:55 UTC | 62 | 61.7 | 0° 0 kt | 1005.1 | RA | |
| 00:15 UTC | 62 | 61.5 | 0° 0 kt | 1005.1 | RA |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The Chicago radar (KLOT), 41 km away, was scanning. The volume nearest the touchdown began at 22:28 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.
What was reported nearby
Local storm reports within 60 km of the path, in the three hours either side.
| Time (UTC) | Report | Where | County | Remark |
|---|---|---|---|---|
| 20:10 UTC | TORNADO | 2 Nw Millington | La Salle, IL | PHOTOS AND VIDEO POSTED TO SOCIAL MEDIA SHOW BRIEF TORNADO NORTHWEST OF MILLINGTON. TIME ESTIMATED BY RADAR. |
| 20:15 UTC | TORNADO | 2 Wnw Millbrook | Kendall, IL | CORRECTS PREVIOUS TORNADO REPORT FROM 2 NW MILLINGTON TO 2 WNW MILLBROOK IN KENDALL COUNTY. ADDITIONAL INFORMATION RECEIVED FROM THOSE PROVIDING PHOTOS AND VIDEO ALLOWED REFINEMENT OF LOCATION. NO DAMAGE WAS REPORTED WIT |
| 20:30 UTC | FLASH FLOOD | Oak Forest | Cook, IL | IL DOT REPORTS US-6 CLOSED AT UNDERPASS NEAR IL-50 DUE TO FLOODING. |
| 20:45 UTC | FLOOD | 2 Ese Manhattan | Will, IL | PHOTO SHARED VIA SOCIAL MEDIA OF PRAIRIE CREEK FLOODING BRUNS ROAD AT THE INTERSECTION WITH KANKAKEE STREET. |
| 21:20 UTC | FLOOD | 3 E Manhattan | Will, IL | PUBLIC REPORTS VIA SOCIAL MEDIA OF FLOODING ALONG MANHATTAN-MONEE ROAD AND SCHOOLHOUSE ROAD EAST OF MANHATTAN. |
| 22:03 UTC | FLASH FLOOD | 1 Nne Manhattan | Will, IL | VIDEO AND PHOTOS SHARED TO SOCIAL MEDIA SHOW NUMEROUS ROADWAYS FLOODED AT LEAST 1FT DEEP IN THE MANHATTAN AREA INCLUDING SMITH ROAD AT FOXFORD DRIVE, SMITH ROAD NEAR MCCORMICK WAY, AND SCHOOLHOUSE ROAD NEAR SMITH ROAD. |
| 22:15 UTC | FLOOD | 1 Nw Blackstone | Livingston, IL | 1 FOOT OF WATER ON IL-17 NEAR IL-18. |
| 22:15 UTC | FLOOD | 4 E Oswego | Kendall, IL | MULTIPLE PUBLIC REPORTS OF FLOODED ROADWAYS NEAR 127TH STREET AND COLLINS ROAD NORTHWEST OF PLAINFIELD. |
| 22:26 UTC | TORNADO | 2 Sse Coal City | Grundy, IL | BRAIDWOOD EMA REPORTED BRIEF TORNADO THAT CROSSED REED ROAD WEST OF I-55. TIME ESTIMATED BY RADAR. |
| 22:30 UTC | FLASH FLOOD | 3 N Campus | Livingston, IL | NUMEROUS ROADWAYS CLOSED IN ROUND GROVE TOWNSHIP DUE TO FLOODING. |
| 22:35 UTC | FLOOD | 5 Sw Plainfield | Kendall, IL | 12-18 INCHES OF WATER ON CATON FARM ROAD AND RIDGE ROAD WEST OF JOLIET. |
| 22:48 UTC | FLOOD | 2 Sw New Lenox | Will, IL | FLOODING REPORTED ON NELSON ROAD AT NUMEROUS LOCATIONS. UNKNOWN DEPTH. RELAYED VIA SPOTTERNETWORK. |
| 22:50 UTC | FLOOD | 2 Ene Homer Glen | Cook, IL | WILL-COOK ROAD CLOSED BETWEEN 151ST STREET AND 159TH STREET DUE TO FLOODING. |
| 23:00 UTC | HEAVY RAIN 3 | 4 Sw Plainfield | Kendall, IL | PRIVATE WEATHER STATION SOUTHWEST OF PLAINFIELD REPORTS 3.0 INCHES OF RAIN IN 2 HOURS ENDING AT 6PM. |
| 23:00 UTC | HEAVY RAIN 3.5 | 3 W Minooka | Grundy, IL | PRIVATE WEATHER STATION WEST OF MINOOKA REPORTS 3.5 INCHES OF RAIN IN 2 HOURS ENDING AT 6PM. |
| 23:00 UTC | HEAVY RAIN 3.6 | 5 Wsw Minooka | Grundy, IL | PRIVATE WEATHER STATION SOUTHWEST OF MINOOKA REPORTS 3.6 INCHES OF RAIN IN 2 HOURS ENDING AT 6PM. |
| 23:05 UTC | FLASH FLOOD | 1 Ene Lemont | Cook, IL | MAIN STREET CLOSED DUE TO FLOODING FROM 4TH STREET TO WALKER ROAD EAST OF LEMONT. |
| 23:10 UTC | FLASH FLOOD | 1 N Minooka | Kendall, IL | NUMEROUS REPORTS OF I-80 FLOODED NEAR RIDGE ROAD IN MINOOKA. |
| 23:15 UTC | FLASH FLOOD | Plainfield | Will, IL | PLAINFIELD PD INDICATES VIA SOCIAL MEDIA THAT NUMEROUS ROADWAYS ARE FLOODED ACROSS THE VILLAGE. |
| 23:30 UTC | FLASH FLOOD | 3 Nw Bolingbrook | Will, IL | MULTIPLE VEHICLES STALLED DUE TO FLOODING ALONG NAPER BOULEVARD BETWEEN ROYCE ROAD AND BAILEY ROAD. |
| 23:30 UTC | FLASH FLOOD | 3 Se Naperville | Dupage, IL | SEVERAL FEET OF WATER ON NAPER BOULEVARD NEAR BAILEY ROAD. |
| 23:50 UTC | FLASH FLOOD | 4 Sw Plainfield | Will, IL | VIDEO SHARED VIA SOCIAL MEDIA SHOWS FLOODING MULTIPLE FEET DEEP ON RESIDENTIAL STREETS OFF COUNTY LINE ROAD. |
| 00:00 UTC | FLOOD | 1 Nnw Sugar Grove | Kane, IL | NUMEROUS PUBLIC REPORTS OF FLOODED ROADWAYS IN THE VICINITY OF SUGAR GROVE RELAYED VIA MPING. |
| 00:00 UTC | FLASH FLOOD | 2 Wsw Romeoville | Will, IL | PHOTO SHARED VIA SOCIAL MEDIA SHOWS SEVERAL INCHES OF WATER ON WEBER ROAD AT 135TH STREET. |
| 00:00 UTC | HEAVY RAIN 2.6 | 6 Ssw Naperville | Will, IL | PRIVATE WEATHER STATION REPORTS 2.6 INCHES OF RAIN IN 3-HR ENDING AT 7PM. |
| 00:30 UTC | FLOOD | 2 W Plainfield | Will, IL | MULTIPLE REPORTS OF IL-126 CLOSED WEST OF PLAINFIELD DUE TO FLOODING. |
| 01:11 UTC | FLOOD | 1 W Oak Forest | Cook, IL | NUMEROUS CARS STALLED DUE TO FLOODING AT 159TH STREET AND CENTRAL AVENUE. DEPTH UNKNOWN. RELAYED VIA AMATEUR RADIO OPERATOR. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2020 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are
The other tornadoes of May 17, 2020
7 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| May 17 | 3:15 PM CDT | Unrated | Kendall, IL | 0.7 | 25 | |||
| May 17 | 4:06 PM CDT | EF0 | Macon, IL | 4.0 | 75 | $10,000 | ||
| May 17 | 5:41 PM CDT | EF1 | Allen Parish, LA | 4.3 | 25 | $10,000 | ||
| May 17 | 6:01 PM CDT | EF0 | Cameron Parish, LA | 1.0 | 10 | |||
| May 17 | 6:40 PM CDT | EF0 | Calcasieu Parish, LA | 0.1 | 10 | |||
| May 17 | 8:00 PM CDT | EF0 | Evangeline Parish, LA | 0.2 | 10 | |||
| May 17 | 8:31 PM CDT | EF3 | Acadia Parish, LA | 3.9 | 100 | 1 | 9 | $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.