A large upper low pressure area in the southwest United States spun off a strong upper level disturbance into the northern plains. This disturbance lifting over the area along with a north to south frontal boundary, powerful low level winds, and abundant gulf moisture resulted in training thunderstorms across northeast South Dakota. The training thunderstorms produced anywhere from 3 to 10 inches of rainfall resulting in widespread flash flooding across Brown, Buffalo, Hand, Spink, Clark, Day, and Marshall counties. Brown, Buffalo, Clark, Day, Marshall, Spink were declared disaster areas by President Bush.

Flash Flood in CLARK, SOUTH DAKOTA
From 05-MAY-07 15:45:00 to 06-MAY-07 09:15:00 (CST-6)
Location: WILLOW LAKE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Very heavy rains of 3 to nearly 7 inches fell across much of Clark county causing flash flooding. Many roads were flooded and damaged with a bridge washed out south of Carpenter. Many homes received water in their basements which resulted in damage for some. Also, thousands of acres of cropland were flooded with many seeds and large quantities of fertilizer washed away.
Rainfall amounts included 4 to 5 inches in the Vienna/Willow Lake area, 5.7 inches in Garden City, 6.72 inches in Clark, and 7.35 inches in Carpenter.

Flash Flood in HAND, SOUTH DAKOTA
From 05-MAY-07 17:33:00 to 06-MAY-07 09:15:00 (CST-6)
Location: DANFORTH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Very heavy rains of 3 to 5 inches fell across much of southern and eastern Hand County causing flash flooding. Many roads along with some homes were damaged by the flooding. Many acres of cropland were also damaged with seeds and fertilizer washed away. Rainfall amounts included 3.65 inches at Miller and 5.10 inches north of Danforth.

Flash Flood in CLARK, SOUTH DAKOTA
From 05-MAY-07 15:45:00 to 06-MAY-07 09:15:00 (CST-6)
Location: WILLOW LAKE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Very heavy rains of 3 to nearly 7 inches fell across much of Clark county causing flash flooding. Many roads were flooded and damaged with a bridge washed out south of Carpenter. Many homes received water in their basements which resulted in damage for some. Also, thousands of acres of cropland were flooded with many seeds and large quantities of fertilizer washed away.
Rainfall amounts included 4 to 5 inches in the Vienna/Willow Lake area, 5.7 inches in Garden City, 6.72 inches in Clark, and 7.35 inches in Carpenter.

Flash Flood in BUFFALO, SOUTH DAKOTA
From 05-MAY-07 20:05:00 to 06-MAY-07 09:15:00 (CST-6)
Location: FT THOMPSON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Very heavy rains of 3 to 6 inches occurred across much of Buffalo county causing flash flooding. Many roads and some homes were flooded with damage resulting. Buffalo county was a declared a disaster area by President Bush. Gann Valley received 6.33 inches of rain.

Flash Flood in DAY, SOUTH DAKOTA
From 05-MAY-07 18:35:00 to 06-MAY-07 09:15:00 (CST-6)
Location: ANDOVER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Very heavy rains of 3 to 6 inches fell across much of Day County causing flash flooding. Many roads were damaged and several were washed out. Many homes received water in their basements with some damage occurring. Also, thousands of acres of cropland were inundated with seeds and fertilzer washed away.
Rainfall amounts included 4.47 inches at Andover, and 4.90 inches at Webster.

Flash Flood in SPINK, SOUTH DAKOTA
From 05-MAY-07 19:18:00 to 06-MAY-07 09:15:00 (CST-6)
Location: TULARE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Very heavy rains of 3 to 8 inches fell within a 6 to 10 hour period across most of Spink county causing widespread flash flooding. Most of the cities in Spink county received some flash flooding including Tulare, Ashton, Redfield, Mellette, Conde, Northville, and Frankfort. Over one-hundred fifty homes, some businesses, and countless roads were flooded. Flooding damage ranged from minor to major damage for homes and roads throughout Spink County. Several bridges were also washed out. A large sinkhole formed in Frankfort from a collapsed sewer line. Basement water levels ranged from a few inches to up to the first floor of some homes. Sewers backed up into homes, some vehicles stalled, and some power outages also occurred. Thousands of acres of crops were flooded and damaged with many seeds and large quantities of fertilizer washed away.
An emergency operations center was operated in Aberdeen for several days to coordinate all emergency activities. Hundreds of volunteers helped with the cleanup. The Governor was in Aberdeen and declared a state of emergency for Spink county.
Spink county was declared a disaster area by President Bush with disaster recovery and community assistance centers opened. Eight damage assessment teams from local, state, and FEMA came to Spink and other counties.
Some rainfall amounts included 5.82 inches at Conde, 7.41 inches at Ashton, 7.55 inches near Mellette, and 8.02 inches at Redfield.

Flash Flood in MARSHALL, SOUTH DAKOTA
From 05-MAY-07 20:30:00 to 06-MAY-07 09:15:00 (CST-6)
Location: LANGFORD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Very heavy rains of 3 to 7 inches caused flash flooding across much of Marshall county. Many roads were flooded with some receiving damage. Also, many homes received water in their basements with some damage. Thousands of acres of cropland were inundated with some seeds and large amounts of fertilizer washed away.
Rainfall amounts included 3.82 inches at Britton, 4 inches at Eden, 5.68 inches west of Britton, 6 inches at Langford, and 7 inches 7 miles west of Britton.

Flash Flood in BROWN, SOUTH DAKOTA
From 05-MAY-07 18:25:00 to 06-MAY-07 09:15:00 (CST-6)
Location: WARNER
Flood cause: Heavy Rain
Property damage: 5.00M
Crop damage: 0.00K
Reported by: Emergency Manager

Very heavy rains of 5 to nearly 10 inches fell within a 6 to 10 hour period across most of Brown county causing widespread flash flooding. Most of the cities affected included Aberdeen, Warner, Columbia, Hecla, Groton, Barnard, Bath, and Stratford. Several hundred homes, some businesses, and countless roads were affected by the flooding. Aberdeen received the most extensive damage, especially the north side of Aberdeen. Seventy-five percent of the homes in Aberdeen received some water in their basements. Basement water levels ranged from a few inches to very deep water all the way up to the first floor of homes. Several homes had basement walls that collapsed. The overwhelming load on the drainage system caused sewage to back up into many homes. The National Guard brought large generators and pumps to Aberdeen to alleviate pressure on the storm system. A school in north Aberdeen was closed for several days because in was surrounded by water. Also, many vehicles stalled on the roads and power outages occurred, mainly in northern Aberdeen, as transformers went under water. Many cars were also damaged by the flooding. Over thirty families in Aberdeen were displaced from their homes with many living in emergency shelters.
Over one-hundred homes in Aberdeen were condemned with nearly fifty considered as unlivable. Thousands of acres of crops were flooded and  damaged with many seeds and large quantities of fertilizer washed away.
An emergency operations center was operated in Aberdeen for several days to coordinate all emergency activities. Hundreds of volunteers helped with the cleanup. Over 2500 tons of flooding debris was taken to the landfill in Aberdeen. The Governor was in Aberdeen and declared a state of emergency for Brown county.
Groton, Stratford, Bath, Claremont, and Columbia also had flooded homes and basements. Thirty percent of Columbia's homes had some water in them with two collapsed basement walls. Eighty percent of Groton's homes had water in their basement with half having sewer backups. Sixty homes in Groton had major damage. Many sewer backups also occurred in Claremont.
Senator John Thune and representative Stephanie Herseth came to Brown County to survey the damage. Brown County was declared a disaster area by President Bush with disaster recovery and community assistance centers opened. Eight damage assessment teams from local, state, and FEMA came to Brown and other counties.
Rainfall amounts included 4.99 inches at Westport, 7.49 inches at Stratford, 7.97 inches at Aberdeen, 8.07 inches at Sand Lake Wildlife Refuge, 8.73 inches at Columbia, and 8.74 inches at Groton. Adding in the previous days rain, Aberdeen received 9.00 inches, Columbia received 10.19 inches, with 10.74 inches at Groton. The 8.74 inches of rainfall at Groton set a new 24 hour state rainfall record.