Illinois, 1998

Flash Flooding in Illinois, May 6, 1998

May 6, 1998 · NWS LOT · 3 events in 3 counties and zones

Strong thunderstorms moved through northeast Illinois during the afternoon, producing heavy rainfall across the area. 10 inches of rain in 45 minutes had flooded an underpass.

Where it happened

Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

  • Tornadoes
  • Tropical storms and surge
  • Floods
  • Wind
  • Hail
  • Winter weather
  • Heat and drought
  • Cold
  • Fire, smoke and dust
  • Marine and coastal
  • Other

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The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
3

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS LOT wrote it up.

Strong thunderstorms moved through northeast Illinois during the afternoon, producing heavy rainfall across the area. A cooperative observer at Matteson, in southern Cook County, reported 3.10 inches of rain in 45 minutes had flooded an underpass. Flooding was also reported in Orland Park, in southern Cook County. Near Park Forest flooding occurred along Thorn Creek in a Forest preserve and some roads were flooded.In southern Grundy County, 1 inch of rain fell in 20 minutes in Mazon and hail, a half-inch in diameter, was reported in Coal City. Radar estimated between 1 and 2 inches of rain had fallen in southern Grundy and Will counties.

The radar

The Chicago radar (KLOT), 49 km away, was scanning. The volume nearest the first event began at 18:44 UTC.

Open the radar archive at this moment

Event by event

3 flash flood. Local standard time, as filed.

Flash Flood, Cook

When
May 6, 12:45 PM CST to 3:00 PM CST
Where
Cook County, South Portion
Coordinates
41.895, -87.646 (the zone’s center; the record gives no point)

Flash Flood, Grundy

When
May 6, 12:45 PM CST to 3:00 PM CST
Where
Grundy County, South Portion
Coordinates
41.285, -88.418 (the zone’s center; the record gives no point)

Flash Flood, Will

When
May 6, 12:45 PM CST to 3:00 PM CST
Where
Will County, South Portion
Coordinates
41.445, -87.979 (the zone’s center; the record gives no point)

What these are

Flash Flood
Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Illinois in 1998Every state in 1998This day in weather historyWarnings in Illinois, May 1998

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5651930, 5651931, 5651932.