Flash Flooding and Flooding in Wisconsin, May 16 to 17, 1999

Name: Flash Flooding and Flooding in Wisconsin, May 16 to 17, 1999
Start: 1999-05-16T14:45
End: 1999-05-17T05:00
Location: Wisconsin

May 16 to 17, 1999 · NWS MKX · 38 events in 14 counties and zones

Where it happened

Every event with a place to put it; 21 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: 1
Property damage: $1.3 million
Crop damage: $1.1 million
Events: 38

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.

Late afternoon thunderstorms rumbled across southern Wisconsin producing classic severe weather damage in many locations. There were numerous reports of wind damage to trees and power lines, large hail, and lightning. One injury was reported when lightning struck a man in Washington county in the city of West Bend. The havoc increased in intensity overnight, mainly in the form of flooding.Several counties had urban/small stream flooding thanks to 2 to 3 inch rainfalls that left water 1 to 3 feet deep inn low spots on roads and underpasses. But flash flooding also developed...with 5 to 7 inches measured in the southern third of Lafayette county during the overnight hours. Several Lafayette County roads had pavement and/or shoulder washouts, and several others were closed. The area around Oregon in Dane county received 4.8 inches in 6 hours, between 11pm and 5 am. Eighteen Oregon homes sustained damage, with 12 homes of them evacuated. There were some road washouts in the Oregon area due to flash flooding. In Green county the Sugar River at Brodhead rose 3.13 feet over the 5 foot flood stage, and was above flood stage through May 21st. The Pecatonica River near Martintown in southwest Green County rose 5.49 feet over its flood stage of 11 feet. It was above flood stage through the 26th of the month. In addition, 5 bridges were washed out near the city of Brooklyn. Rainfall amounts across Green County were in the 3 to 5 inch range. The city of Jefferson in Jefferson county measured 4.1 inches of rain in 2 hours, a 100 year rainfall for that location. The resultant flash flood damaged the interior and exterior of 5 schools which were all closed on the 17th. The southwest part of the city of Milwaukee experienced a flash flood that completely flooded underpasses, stalled dozens of vehicles, caused hillside erosion, undermined some roads, and caused a 10 vehicle crash at the I-43 and Highway 100 intersection. Spotty, county-wide road washouts and severe erosion were noted in Iowa County due to local flash flooding in the wake of 3 to 5 inches of rain within 2 to 3 hours. Along with the heavy rains a microburst with winds estimated at 70 mph caused minor damage to several homes near Emerald Grove (Rock Co.) and collapsed a farm outbuilding. Another downburst struck the south side of Janesville (Rock Co.), damaging the roofs of 3 businesses, flipping over 3 storage tanks, and overturning a semi truck. The powerful downburst winds which hit the Wheatland area (Kenosha Co.), damaged a school roof, and then damaged a roof and window of a home across the street. LIghtning in the Madison area (Dane Co.) resulted in one serious home fire, and damage to 5 vehicles at a car dealership. Four Milwaukee (Milwaukee Co.) homes were struck by lightning and experienced minor fires. In the city of Janesville, lightning started a fire in an apartment building. In West Bend (Washington Co.) lighting struck a home under construction, resulting in a significant fire. There were other scattered reports of lightning striking homes or businesses, resulting in minor fires. At one time or another, about 13,000 electrical customers in southcentral and southeast Wisconsin were without power due to lightning striking lines or transformers.

The radar

The La Crosse radar (KARX), 124 km away, was scanning. The volume nearest the first event began at 20:42 UTC.

Open the radar archive at this moment

Event by event

12 thunderstorm wind, 11 lightning, 6 flash flood, 5 hail, 4 flood. Local standard time, as filed.

Thunderstorm Wind, Iowa

When: May 16, 2:45 PM CST
Where: Iowa County, 3 mi W of Dodgeville
Property damage: $1,000
Reported by: DEPT OF HIGHWAYS
Coordinates: 42.970, -90.200

Thunderstorm Wind, Sauk

When: May 16, 3:20 PM CST
Where: Sauk County, Reedsburg
Property damage: $1,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.530, -90.000

Hail, Iowa

When: May 16, 3:30 PM CST
Where: Iowa County, Barneveld
Measured: 1 in hail
Reported by: AMATEUR RADIO
Coordinates: 43.020, -89.900

Thunderstorm Wind, Dane

When: May 16, 3:50 PM CST
Where: Dane County, Blue Mounds
Property damage: $1,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.020, -89.830

Thunderstorm Wind, Dane

When: May 16, 4:12 PM CST
Where: Dane County, Madison
Property damage: $2,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.070, -89.420

Lightning, Dane

When: May 16, 4:15 PM CST
Where: Dane County, Madison
Property damage: $150,000
Reported by: EMERGENCY MANAGER
Coordinates: 43.067, -89.418 (the zone’s center; the record gives no point)

Hail, Jefferson

When: May 16, 4:38 PM CST
Where: Jefferson County, 2 mi S of Lake Mills
Measured: 1 in hail
Reported by: AMATEUR RADIO
Coordinates: 43.050, -88.900

Flood, Waukesha

When: May 16, 5:00 PM CST to 7:00 PM CST
Where: Waukesha County, Brookfield
Reported by: NEWSPAPER
Coordinates: 43.018, -88.304 (the zone’s center; the record gives no point)

Flood, Rock

When: May 16, 5:15 PM CST to 7:00 PM CST
Where: Rock County, Evansville
Reported by: NEWSPAPER
Coordinates: 42.671, -89.072 (the zone’s center; the record gives no point)

Thunderstorm Wind, Washington

When: May 16, 5:25 PM CST
Where: Washington County, West Bend
Measured: 52 kt (60 mph)
Property damage: $4,000
Reported by: NEWSPAPER
Coordinates: 43.420, -88.180

Flood, Ozaukee

When: May 16, 5:30 PM CST to 6:30 PM CST
Where: Ozaukee County, Grafton
Reported by: NEWSPAPER
Coordinates: 43.403, -87.891 (the zone’s center; the record gives no point)

Thunderstorm Wind, Racine

When: May 16, 5:35 PM CST
Where: Racine County, Waterford
Measured: 56 kt (64 mph)
Reported by: TRAINED SPOTTER
Coordinates: 42.770, -88.220

Lightning, Walworth

When: May 16, 5:55 PM CST
Where: Walworth County, Williams Bay
Property damage: $3,000
Reported by: NEWSPAPER
Coordinates: 42.669, -88.542 (the zone’s center; the record gives no point)

Lightning, Walworth

When: May 16, 5:55 PM CST
Where: Walworth County, Williams Bay
Property damage: $3,000
Reported by: NEWSPAPER
Coordinates: 42.669, -88.542 (the zone’s center; the record gives no point)

Lightning, Milwaukee

When: May 16, 6:00 PM CST
Where: Milwaukee County, Milwaukee
Property damage: $4,000
Reported by: NEWSPAPER
Coordinates: 43.022, -87.929 (the zone’s center; the record gives no point)

Lightning, Milwaukee

When: May 16, 6:00 PM CST
Where: Milwaukee County, Milwaukee
Property damage: $4,000
Reported by: NEWSPAPER
Coordinates: 43.022, -87.929 (the zone’s center; the record gives no point)

Thunderstorm Wind, Kenosha

When: May 16, 6:25 PM CST
Where: Kenosha County, Wheatland
Property damage: $38,000
Reported by: NEWSPAPER
Coordinates: 42.600, -88.200

Flash Flood, Milwaukee

When: May 16, 6:30 PM CST to 9:00 PM CST
Where: Milwaukee County, Milwaukee
Property damage: $25,000
Reported by: NEWSPAPER
Coordinates: 43.022, -87.929 (the zone’s center; the record gives no point)

Flood, Kenosha

When: May 16, 6:30 PM CST to 8:00 PM CST
Where: Kenosha County, Kenosha
Reported by: NEWSPAPER
Coordinates: 42.573, -87.840 (the zone’s center; the record gives no point)

Thunderstorm Wind, Milwaukee

When: May 16, 6:55 PM CST
Where: Milwaukee County, Oak Creek
Measured: 54 kt (62 mph)
Property damage: $1,000
Reported by: TRAINED SPOTTER
Coordinates: 42.870, -87.870

Hail, Kenosha

When: May 16, 6:55 PM CST
Where: Kenosha County, 3 mi W of Kenosha
Measured: 1.75 in hail
Property damage: $1,000
Reported by: AMATEUR RADIO
Coordinates: 42.580, -87.900

Hail, Lafayette

When: May 16, 8:20 PM CST
Where: Lafayette County, 2 mi NE of Benton
Measured: 1 in hail
Reported by: AMATEUR RADIO
Coordinates: 42.580, -90.350

Thunderstorm Wind, Iowa

When: May 16, 9:00 PM CST
Where: Iowa County, 3 mi N of Dodgeville
Property damage: $1,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.020, -90.130

Hail, Lafayette

When: May 16, 9:22 PM CST
Where: Lafayette County, South Wayne
Measured: 1 in hail
Reported by: AMATEUR RADIO
Coordinates: 42.570, -89.880

Flash Flood, Iowa

When: May 16, 9:30 PM CST to 11:59 PM CST
Where: Iowa County, Countywide
Property damage: $50,000
Reported by: EMERGENCY MANAGER
Coordinates: 43.001, -90.135 (the zone’s center; the record gives no point)

Flash Flood, Lafayette

When: May 16, 9:30 PM CST to 11:59 PM CST
Where: Lafayette County, South Portion
Property damage: $250,000
Crop damage: $500,000
Reported by: EMERGENCY MANAGER
Coordinates: 42.661, -90.132 (the zone’s center; the record gives no point)

Flash Flood, Dane

When: May 16, 10:00 PM CST to May 17, 1:00 AM CST
Where: Dane County, 2 mi WSW of Oregon
Property damage: $100,000
Reported by: EMERGENCY MANAGER
Coordinates: 43.067, -89.418 (the zone’s center; the record gives no point)

Flash Flood, Green

When: May 16, 10:45 PM CST to May 17, 1:00 AM CST
Where: Green County, Countywide
Property damage: $120,000
Crop damage: $600,000
Reported by: NEWSPAPER
Coordinates: 42.680, -89.602 (the zone’s center; the record gives no point)

Lightning, Rock

When: May 16, 11:10 PM CST
Where: Rock County, Janesville
Property damage: $40,000
Reported by: NEWSPAPER
Coordinates: 42.671, -89.072 (the zone’s center; the record gives no point)

Lightning, Rock

When: May 16, 11:10 PM CST
Where: Rock County, Janesville
Property damage: $40,000
Reported by: NEWSPAPER
Coordinates: 42.671, -89.072 (the zone’s center; the record gives no point)

Thunderstorm Wind, Rock

When: May 17, 12:07 AM CST
Where: Rock County, 1 mi S of Emerald Grove
Measured: 61 kt (70 mph)
Property damage: $75,000
Reported by: NEWSPAPER
Coordinates: 42.650, -88.880

Thunderstorm Wind, Rock

When: May 17, 12:25 AM CST
Where: Rock County, Janesville
Property damage: $175,000
Reported by: NEWSPAPER
Coordinates: 42.680, -89.020

Lightning, Washington

When: May 17, 12:40 AM CST
Where: Washington County, West Bend
Injuries: 1 direct, 0 indirect
Property damage: $35,000
Reported by: NEWSPAPER
Coordinates: 43.369, -88.231 (the zone’s center; the record gives no point)

Thunderstorm Wind, Walworth

When: May 17, 12:40 AM CST
Where: Walworth County, Walworth to La Grange
Property damage: $3,000
Reported by: NEWSPAPER
Coordinates: 42.530, -88.600

Lightning, Dane

When: May 17, 12:40 AM CST
Where: Dane County, Madison
Property damage: $110,000
Reported by: NEWSPAPER
Coordinates: 43.067, -89.418 (the zone’s center; the record gives no point)

Lightning, Waukesha

When: May 17, 1:20 AM CST
Where: Waukesha County, Oconomowoc
Property damage: $2,000
Reported by: NEWSPAPER
Coordinates: 43.018, -88.304 (the zone’s center; the record gives no point)

Lightning, Milwaukee

When: May 17, 1:30 AM CST
Where: Milwaukee County, Greenfield
Property damage: $50,000
Reported by: NEWSPAPER
Coordinates: 43.022, -87.929 (the zone’s center; the record gives no point)

Flash Flood, Jefferson

When: May 17, 2:00 AM CST to 5:00 AM CST
Where: Jefferson County, Jefferson
Property damage: $30,000
Reported by: NEWSPAPER
Coordinates: 43.021, -88.776 (the zone’s center; the record gives no point)

What these are

Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Lightning: A lightning strike that killed, injured or caused damage.
Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.
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 Wisconsin in 1999 Every state in 1999 This day in weather history Warnings in Wisconsin, May 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: 5698525, 5698526, 5698528, 5698527, 5698529, 5698530, 5698616, 5698633, 5698636, 5698617, 5698634, 5698619, 5698639, 5698643, 5698642, 5698644, 5698620, 5698635, 5698637, 5698621, 5698622, 5698623, 5698624, 5698627, 5698625, 5698626, 5698628, 5698629, 5698640, 5698645, 5698630, 5698631, 5698618, 5698632, 5698641, 5698646, 5698647, 5698638.