Mahaska County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Mahaska County: 1.
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.

Claims by ZIP code

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 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, Mahaska$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. Aug 1, 2010Flood$1.0 million
   National Weather Service narrative

   Flooding continued along a large part of the Des Moines River Basin from the previous month. The flooding ended in the Stratford area by the afternoon of the 1st, however releases from Saylorville and Red Rock Reservoirs maintained river stages above flood stage through the first week of the month in the Des Moines area, and through the month in the Eddyville and Ottumwa areas.

3. Oct 26, 1997Heavy Snow, Mahaska$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…

4. May 24, 1996Hail$530,000
   National Weather Service narrative

   As the thunderstorms moved across the Oskaloosa area, considerable damage was done to a 4.5 acre greenhouse complex north of town. Damage to the complex was nearly one half million dollars.

5. Feb 24, 2007Winter Storm, Mahaska$500,000
   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…

6. Jun 17, 1996Flood, Mahaska$500,000
   National Weather Service narrative

   The wet weather conditions experienced during the month of May carried into June. Preliminary information provided by the State Climatologist Harry Hillaker, Iowa Department of Agriculture and Land Stewardship, indicated a statewide rainfall average of 5.04 inches during the month of June. This is 114% of the normal. Strong thunderstorms with locally torrential rain moved through parts of central and north central Iowa beginning on the evening of the 16th. Rainall amounts in excess of 3 inches were common over large parts of the area, with point rainfall as high as 9 inches over the Skunk River and Squaw Creek basins upstream of Ames. The resulting flood was the third highest…

7. Aug 10, 2010Flash Flood$500,000
   National Weather Service narrative

   Water receding but still flooding in Oskaloosa. Numerous houses inundated in town with 18 people rescued.

8. Sep 30, 2007Tornado$500,000
   National Weather Service narrative

   Tornado moved into Mahaska County from Marion County, then continued northeast into Jasper County.|

9. Jun 25, 2000Flash Flood$500,000
   National Weather Service narrative

   A major wind and significant flash flooding event took shape across Iowa during the afternoon and evening of the 25th. A dynamic upper level system approached Iowa from the northwest during the afternoon. Several boundaries were in the area resulting from weak convection that took place during the morning. Very strong theta-e advection took place over northeast Nebraska during the morning and early afternoon hours. In addition, several other factors came into play. Moisture continued to stream into Iowa from the remnants of Hurricane Carlotta as precipitable water values approached 2.2 inches. Iowa was also under the influence of a coupled jet structure. As a result a strong upper…

10. May 9, 1996Flash Flood$500,000
    National Weather Service narrative

    Heavy rainfall occurred in Mahaska County as thunderstorms rolled across. Rainfall amounts ranged from 3 inches ove the southern part of the county, upwards to 8 inches over the north. All of the rain fall in a few hours time. Many basements were flooded in the town of Oskaloosa. Flash flooding was widespread across the county. Highway 92 was closed for a time as water overtopped the highway.

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

106°FJul 23, 2012

All-time low

−27°FFeb 3, 1996

Warmest night

84°FAug 17, 1983

Coldest day

−14°FFeb 2, 1996

Wettest day

5.32 inSep 14, 1992

Snowiest day

15.0 inFeb 13, 1978

Hottest year

1987mean 54.3°F

Coldest year

2014mean 47.8°F

Wettest year

199854.52 in

Driest year

195319.09 in

Snowiest season

63.9 in1977-78

Station Ottumwa Ind Airport (USW00014950), 834 ft elevation, 17.8 miles from the population centre. Daily records from 1948 to October 16, 2026; 98.9% 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 USW00014950.
• 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.