Poweshiek County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Poweshiek County: 4.
2. Weak tornadoes were under-recorded before Doppler radar coverage became national in the early 1990s, so earlier decades read low. Ratings use the Fujita scale before February 2007 and the Enhanced Fujita scale after.

Storm Prediction Center severe weather database, 1950 to 2025.

Smoke overhead

1. A smoke day is a date on which a smoke plume traced by NOAA Hazard Mapping System analysts from satellite imagery covered this place's point (the county's population centre or the city centre). Counts here are of medium or heavy smoke. Since 2018 analysts have often drawn light smoke as one area over most of the continent, so light-smoke counts are not comparable from year to year. The plumes show smoke anywhere in the air above, not air quality at the ground, and smoke hidden by cloud is missed.

NOAA Hazard Mapping System smoke analysis, 2011 to 2026, retrieved October 30, 2026.

OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026. NOAA Storm Events through 2026.

River crests

River gauges

1. Crests are the highest and the recent crests the National Weather Service lists for each river gauge in the county that has a flood stage, not every flood. Flood categories use each gauge's current flood stages; crests from before levees, dams or channel changes may not be comparable. Crests measured on an old datum are left out of the rankings.

NOAA National Water Prediction Service gauge records, retrieved October 30, 2026.

1. The Palmer Drought Severity Index is computed by NOAA each month from the county's average temperature and precipitation, relative to the county's own climate. Zero is normal; -3 or lower is severe drought and -4 or lower extreme drought. It describes the long-term balance of moisture, not water supply or crop losses.

NOAA NCEI nClimDiv county Palmer Drought Severity Index, 1895 to September 2026, issued October 6, 2026.

More event types since 1996

Costliest events since 1996

1. Aug 1, 2003Drought, Poweshiek$12.7 million
   National Weather Service narrative

   Dry weather settled in over Iowa during the month. The last widespread rain occurred on 09 July. With the increasingly dry conditions became a primary concern as the month progressed. An extended period of heat and humidity from the 15th to 25th saw highs into the 90s to over 100 degrees F. in some locations. By month's end drought indices had worsened to severe to extreme drought across south central Iowa and at least moderate drought over the remainder of the HSA. Waterloo had its driest August on record, Des Moines its 3rd driest and Ottumwa its 8th driest. A cold front brought only a brief respite from the intense heat, as temperatures rebounded into the 90s to near 100…

2. Apr 6, 2010Thunderstorm Wind$3.0 million
   National Weather Service narrative

   On the north edge of Grinnell, cars were reported off the road and flipped. Power lines were down and roofs were blown off homes.

3. Sep 30, 2007Tornado$2.5 million
   National Weather Service narrative

   Tornado moved into Poweshiek County from Jasper County. It lifted west of Malcom.|

4. Feb 24, 2007Winter Storm, Poweshiek$1.0 million
   National Weather Service narrative

   A major winter storm affected Iowa through the 24th and 25th of February. A powerful upper low moved onto the west coast during the middle of the week, and advanced east through the Rockies during the end of the week. Strong warm air advection took place over the top of a shallow polar airmass that was in place over Iowa. The east-southeasterly flow at the surface drew cool and dry air into the state from the east, setting the stage for a significant ice storm. The main area of precipitation overspread the state during the early morning hours of the 24th and persisted through much of the 25th. Initially, very warm air aloft meant that the precipitation fell in the form of freezing…

5. Oct 26, 1997Heavy Snow, Poweshiek$640,000
   National Weather Service narrative

   The first major winter storm of the season developed over the central Rockies as a powerful upper level jet stream dove into the southern Rockies. Intense low pressure developed over northern Oklahoma, then drifted northeast on the early morning of the 26th. A cold high pressure of Arctic origin was poised to the north of Iowa. The high gradually pushed cold air south into the central U.S. causing the precipitation on the northwest edge of the storm system to change to snow. During the early morning hours, the system went convective with widespread "thundersnow" reported over the south half of Iowa. Lightning struck a tree outside of a house in Nevada causing damage to electrical…

6. Jun 26, 2010Lightning$550,000
   National Weather Service narrative

   A very unstable airmass was in place over western Iowa and areas to the west. CAPE rose to over 6500 J/kg by late afternoon with the lifted indices falling to -12 to -15 C. Downdraft CAPE as quite high at around 1600 J/kg, while available CAPE in the -10 to -30 C layer of the atmosphere was between 700 and 1000 J/kg. The atmosphere had a strong shear present with 40 to 60 kts The freezing level was quite high, just below 15,000 feet. Precipitable water increased to around 1.5 inches. Strong thunderstorms developed over southern Minnesota. Initially, the thunderstorms moved east. Once they became more rooted in the boundary layer, they moved southeast and propagated nearly due…

7. Apr 6, 2010Hail$500,000
   National Weather Service narrative

   The frontal boundary from the previous night lifted north as a warm front as low pressure over Kansas pushed northeast into Iowa. The low eventually tracked from southwest Iowa in the afternoon to east central Iowa by early evening. To the southeast of the front, temperatures warmed into the upper 70s to mid 80s, with dew point temperatures in the upper 50s to mid 60s. The atmosphere became quite unstable with lifted indices falling to -5 to -8 Celsius and CAPE rising to 2000-3000 J/kg. The situation was very dynamic with a synoptic scale upper level trough to the west and broad southwest flow over the central U.S. The jet at 300 mb was around 100 kts with 500 mb winds southwest…

8. Nov 10, 1998High Wind, Poweshiek$300,000
   National Weather Service narrative

   Iowa experienced the worst November storm system since the great storm of 9 and 10 November 1975. During the 9th, low pressure developed over southeast Colorado. The low moved across Kansas during the afternoon and evening of the 9th and deepened to about 990 mb. Warm and moist air was drawn north ahead of the low resulting in widespread across the state. Thunderstorms erupted during the late evening of the 9th, though no severe weather occurred. During the predawn hours of the 10th, a jet streak rotated around the base of the upper level low pressure area. The jet stream, combined with a tropospheric fold, resulted in explosive deepening of the low. As the low moved through…

9. May 26, 2013Flood$250,000
   National Weather Service narrative

   Numerous road closings due to flooding throughout Poweshiek County including 400th Ave west of Grinnell and several roads in the Searsboro and Montezuma area.

10. Sep 30, 2007Tornado$250,000
    National Weather Service narrative

    The second tornado touched down northwest of Malcom. This tornado was on the ground for about 5 miles before lifting north of town.

1. Storm Events records before 1996 cover only tornadoes, thunderstorm wind and hail. Damage figures are as reported by the National Weather Service at the time, not adjusted for inflation.

NOAA NCEI Storm Events Database, 1950 to 2026, issued October 26, 2026.

All-time high

107°F2 times, most recently Aug 3, 1930

All-time low

−35°F2 times, most recently Feb 4, 1996

Warmest night

84°F2 times, most recently Jul 31, 1917

Coldest day

−13°FFeb 3, 1996

Wettest day

6.92 inAug 5, 1970

Snowiest day

12.0 in3 times, most recently Dec 9, 2009

Hottest year

1922mean 52.2°F

Coldest year

1979mean 44.2°F

Wettest year

201057.51 in

Driest year

198817.53 in

Snowiest season

63.3 in1978-79

Station Grinnell 3 Sw (USC00133473), 915 ft elevation, 6.5 miles from the population centre. Daily records from 1893 to October 27, 2026; 91.0% of days in the last 30 years are complete. Records at a single station can differ from a city’s official threaded record, which may combine several stations.

NOAA NCEI Global Historical Climatology Network Daily.

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA Disaster Declarations Summaries, retrieved October 30, 2026. Statewide declarations are not listed.

Neighbouring counties

• Tornadoes NOAA Storm Prediction Center severe weather database, through 2025.
• Tropical cyclones NOAA National Hurricane Center HURDAT2 (Atlantic; Northeast and Central Pacific), through 2025.
• Wildfire USGS/USFS Monitoring Trends in Burn Severity, through 2026.
• Storm events NOAA NCEI Storm Events Database, through 2026.
• Flood insurance OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026.
• Declarations OpenFEMA Disaster Declarations Summaries v2, retrieved October 30, 2026.
• Weather records NOAA NCEI Global Historical Climatology Network Daily, station USC00133473.
• River crests NOAA National Weather Service, National Water Prediction Service river gauges, retrieved October 30, 2026.
• Drought NOAA NCEI nClimDiv county Palmer Drought Severity Index, through September 2026.
• Smoke NOAA NESDIS Hazard Mapping System smoke analysis, retrieved October 30, 2026.
• Earthquakes USGS ANSS Comprehensive Earthquake Catalog (ComCat), retrieved October 30, 2026.

Joins, thresholds and known limits are set out in the methodology. Found an error? Report it. Page built October 30, 2026.