An upper level low pressure dropped south out of Minnesota into Iowa during the night. Though the airmass over Iowa was typical of early to mid July, however the upper level low pressure was more typical of the cold season.
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.
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.
The episode as NWS DMX wrote it up.
An upper level low pressure dropped south out of Minnesota into Iowa during the night. Though the airmass over Iowa was typical of early to mid July, however the upper level low pressure was more typical of the cold season. With abundant moisture in place, rain and embedded thunderstorms developed in bands across the state. Very heavy, nearly tropical, rainfall developed. Six inches of rain fell in just a few hours time over Cerro Gordo County in north central Iowa. In spite of the generally dry conditions recently, flash flooding took place even though not as serious as one would normally expect. Some of the more serious flooding took place south of the Ventura area. A section of road about 100 meters long was washed out in the area by the heavy rain. Other damage around the county was more scattered in nature. Crop damage was somewhat widespread as the heavy rain flattened crops, some of which was beyond recovery. The general rule of thumb is if the corn is leaning more than 30 degrees from true, yield reduction will result. If greater than 45 degrees is is unlikely the farmer would be able to harvest more than silage. The true damage won't be known until sometime in mid to late 2003 however.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Des Moines, IA wrote its last area forecast discussion before the first event at Jul 10, 7:55 PM CST, 2 hours 5 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 855 PM CDT WED JUL 10 2002 GOOD PRESSURE FALLS ACRS EASTERN NEBRASKA HAVE ALLOWED WNDS ACRS CWA TO ONCE AGAIN BECOME SOUTHEASTERLY. HOWEVER...MAIN FOCUS FOR RAINFALL OVERNIGHT APPEARS TO RUN FROM NORTH CENTRAL INTO SOUTHEAST PORTIONS OF THE CWA ALONG AN OLDER AXIS OF CONVERGENCE. STILL... WOULD NOT BE SURPRISED TO SEE A FEW LOCATIONS OF HEAVIER RAIN FARTHER WEST AS UPPER LOW DROPS INTO NORTHERN IA AS ATMOSPHERE REMAINS QUITE MOIST. WL CONTINUE FLOOD WATCH FOR ENTIRE CWA WITH EMPHASIS IN NORTHERN AND EASTERN PORTIONS. .DSM...FLOOD WATCH OVERNIGHT ENTIRE DMX CWA. COGIL
The Des Moines radar (KDMX), 155 km away, was scanning. The volume nearest the first event began at 04:02 UTC.
1 flash flood. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2002Every state in 2002This day in weather historyWarnings in Iowa, July 2002
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: 5304620.