Below normal rainfall continued to allow conditions to deteriorate across portions of south central into southeast Iowa during the month with areas of extreme drought. This was the culmination of both short term dryness and longer term (multi-year) precipitation deficits.
Every event with a place to put it; 7 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.
Below normal rainfall continued to allow conditions to deteriorate across portions of south central into southeast Iowa during the month with areas of extreme drought. This was the culmination of both short term dryness and longer term (multi-year) precipitation deficits.
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 31, 10:45 PM CST, 1 hour 15 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 1145 PM CDT Tue Jul 31 2018 .DISCUSSION.../Tonight through Tuesday/ Issued at 352 PM CDT Tue Jul 31 2018 Other than the thunderstorm activity Wednesday afternoon and evening, generally quiet weather is in store through the end of the work week and into the first part of the weekend wrt to precipitation chances. Hotter temperatures return by Friday through the weekend, but heat index values are not expected to reach criteria levels. The main focus was on a cold front providing convective chances Wednesday afternoon into the evening. Biggest change was increased pops (and expanding them further south) past 21z Wednesday with models suggesting slightly better forcing and moisture available. MUCAPE increases along and north of Interstate 80 to 1500-3000 J/kg during the afternoon Wednesday. Shear is weak, albeit somewhat backing, but with 0-1km shear near 10 knots and 0-6km shear only 15 to 20 knots, low confidence with any widespread severe weather. Thus expecting pulse storms Wednesday afternoon into the early evening. High pressure builds into the region Wednesday night into Thursday and is expected to be centered over the state by Thursday morning over northern Iowa into southern Minnesota. Lowered minimum temperatures Thursday morning over the northern portion of the state as guidance has come in much cooler and with a good radiational cooling night. Dew point depressions near zero by Thursday morning with the radiational cooling setup providing the potential for fog. The main caveat is the depth of the moisture and left out mention attm. The surface high pressure shifts east Friday allowing for southwest return flow into the region. Warm and breezy conditions set into the state Friday into Sunday with Saturday likely the breeziest day as winds near 30 knots atop the mixed layer past 18z Saturday. 850mb temperatures warm to +20C to +22C each afternoon Friday into Sunday. && .AVIATION.../For the 06Z TAFS through 0600Z Wednesday night/ Issued at 1145 PM CDT Tue Jul 31 2018 Little change to the going forecast. VFR conditions still forecast through at least 02/00Z. Main change was to include two rounds of potential storms to northern TAFs. An upper level disturbance will pass across the north into east central Iowa and could kick some storms off mid to late morning. Better chances then as the front comes through in the afternoon/evening. Did also mention some light fog north towards the end of the forecast period. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && DISCUSSION...Podrazik AVIATION...FAB
Hazardous Weather Outlook National Weather Service Des Moines IA 346 PM CDT Tue Jul 31 2018 IAZ028-039-050-062-074-075-083>086-094>097-011100- Bremer-Black Hawk-Tama-Poweshiek-Marion-Mahaska-Clarke-Lucas- Monroe-Wapello-Decatur-Wayne-Appanoose-Davis- 346 PM CDT Tue Jul 31 2018 This Hazardous Weather Outlook is for portions of southern and eastern Iowa. .DAY ONE...This afternoon and tonight Isolated non severe thunderstorms are possible this evening. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Scattered thunderstorms are forecast Wednesday afternoon and evening, mainly across central and northern Iowa. There is a marginal risk of severe weather in those locations with damaging wind the primary threat. Additional intermittent chances for thunderstorms are forecast Saturday through Monday, especially north. The severe weather threat during those periods is uncertain at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed briefly late Wednesday. IAZ004>007-015>017-023>027-033>038-044>049-057>061-070>073-081- 082-092-093-011100- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Sac-Calhoun-Webster- Hamilton-Hardin-Grundy-Crawford-Carroll-Greene-Boone-Story- Marshall-Audubon-Guthrie-Dallas-Polk-Jasper-Cass-Adair-Madison- Warren-Adams-Union-Taylor-Ringgold- 346 PM CDT Tue Jul 31 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Scattered thunderstorms are forecast Wednesday afternoon and evening, mainly across central and northern Iowa. There is a marginal risk of severe weather in those locations with damaging wind the primary threat. Additional intermittent chances for thunderstorms are forecast Saturday through Monday, especially north. The severe weather threat during those periods is uncertain at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed briefly late Wednesday. Small
The national radar mosaic for the moment the first event began.
7 drought. Local standard time, as filed.
Heat and below normal precipitation continued to add to substantial drought conditions across the county. Both crops and agricultural ponds were adversely affected by the lingering precipitation deficits.
Extreme drought conditions persist across much of the county during the month with continuing precipitation deficits.
Extreme drought affect far southeast portions of the county with severe drought elsewhere in the county. Precipitation deficits continued for much of the month.
Severe drought conditions continued across much of Decatur county for the month. Rainfall deficits during the month contributed to crop stress and low agricultural pond levels.
Severe drought conditions persisted during the month across southeast portions of the county. Precipitation deficits remained for much of the month.
Severe to extreme drought conditions persisted across the southern half of Wapello county during the month. Rainfall deficits across the county remained the highest across the south where crop stress was common along with low agricultural pond levels.
Severe to extreme drought was common across Monroe county during the month of August. Rainfall deficits were widespread for much of the month with stress to crops and low to non-existent agricultural pond levels.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2018Every state in 2018This day in weather historyWarnings in Iowa, August 2018
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: 779483, 779484, 779485, 779486, 779487, 779488, 779489.