Flash Flooding in Iowa, July 20, 1999

Name: Flash Flooding in Iowa, July 20, 1999
Start: 1999-07-20T17:50
End: 1999-07-20T22:55
Location: Iowa

July 20, 1999 · NWS ARX · 6 events in 6 counties and zones

Thunderstorms dropped torrential rains on northeast Iowa, which caused a second round of flash floods in as many days. Numerous highways were either closed or remained closed due to high water.

Where it happened

Every event with a place to put it; 6 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

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $1.3 million
Crop damage: $470,000
Events: 6

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 ARX wrote it up.

Thunderstorms dropped torrential rains on northeast Iowa, which caused a second round of flash floods in as many days. Numerous highways were either closed or remained closed due to high water.

The radar

The La Crosse radar (KARX), 154 km away, was scanning. The volume nearest the first event began at 23:50 UTC.

Open the radar archive at this moment

Event by event

6 flash flood. Local standard time, as filed.

Flash Flood, Floyd

When: July 20, 5:50 PM CST to 10:30 PM CST
Where: Floyd County, Countywide
Property damage: $225,000
Crop damage: $100,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.060, -92.789 (the zone’s center; the record gives no point)

Flash Flood, Chickasaw

When: July 20, 6:02 PM CST to 10:45 PM CST
Where: Chickasaw County, Countywide
Property damage: $350,000
Crop damage: $100,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.060, -92.318 (the zone’s center; the record gives no point)

Flash Flood, Mitchell

When: July 20, 7:00 PM CST to 10:55 PM CST
Where: Mitchell County, Countywide
Property damage: $350,000
Crop damage: $120,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.356, -92.789 (the zone’s center; the record gives no point)

Flash Flood, Howard

When: July 20, 7:45 PM CST to 10:55 PM CST
Where: Howard County, Countywide
Property damage: $275,000
Crop damage: $90,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.357, -92.317 (the zone’s center; the record gives no point)

Flash Flood, Fayette

When: July 20, 8:00 PM CST to 10:55 PM CST
Where: Fayette County, West Portion
Property damage: $50,000
Crop damage: $40,000
Reported by: NEWSPAPER
Coordinates: 42.863, -91.844 (the zone’s center; the record gives no point)

Flash Flood, Clayton

When: July 20, 8:30 PM CST to 10:30 PM CST
Where: Clayton County, West Portion
Property damage: $25,000
Crop damage: $20,000
Reported by: NEWSPAPER
Coordinates: 42.845, -91.341 (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

Every storm in Iowa in 1999 Every state in 1999 This day in weather history Warnings in Iowa, July 1999

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: 5707559, 5707558, 5707560, 5707561, 5707562, 5707563.