Wisconsin, 1998

Flash Flood in Wisconsin, August 5, 1998

August 5, 1998 · NWS MKX · 1 event in 1 county or zone

, dumping 3 to 4 inches of rain within a couple hours. The resultant flash flood left damage to about 50 homes in Janesville, washed out gravel road shoulders, and stalled or floated many vehicles.

Where it happened

Every event with a place to put it; 1 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
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  • Winter weather
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  • Cold
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The toll

Deaths
0
Injuries
0
Property damage
$550,000
Crop damage
None recorded
Events
1

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 MKX wrote it up.

A series of thunderstorms, slowly moving northeast at 10 mph, trained through Rock Co., dumping 3 to 4 inches of rain within a couple hours. The resultant flash flood left damage to about 50 homes in Janesville, washed out gravel road shoulders, and stalled or floated many vehicles. Water levels on many roads reached a depth of 1 to 3 feet, and forced the closure of the I-94 exit ramp at Highway 14. Some homes had basement wall damage, while many streets were closed until water levels receded. The synoptic reasons for this flooding can be found in the August 4th entry for flash flooding in Columbia Co.

The radar

The Milwaukee radar (KMKX), 54 km away, was scanning. The volume nearest the first event began at 13:49 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Rock

When
August 5, 7:50 AM CST to 10:30 AM CST
Where
Rock County, Janesville
Property damage
$550,000
Reported by
LAW ENFORCEMENT
Coordinates
42.671, -89.072 (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 Wisconsin in 1998Every state in 1998This day in weather historyWarnings in Wisconsin, August 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: 5664598.