Union County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Union County: 0.
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.

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.

1. Earthquakes of magnitude 2.5 or more in the USGS Comprehensive Catalog since 1900. Within 50 miles means the epicentre lies within 50 miles of the county boundary (or inside the county).
2. Small earthquakes were under-recorded before the modern seismic networks of the 1970s and are still missed in remote areas, so early decades read low. Magnitudes are as the catalogue reports them and mix scales (moment, local and body-wave).

USGS ANSS Comprehensive Earthquake Catalog, 1900 to present, retrieved October 30, 2026.

More event types since 1996

Costliest events since 1996

1. Aug 1, 2003Drought, Union$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 14, 2012Tornado$5.0 million
   National Weather Service narrative

   This tornado continued in from Adams county. NWS storm survey confirmed a strong EF2 tornado. It entered Union county just southwest of Cromwell and tracked east-northeast through the far northwest portion of Creston. The Greater Regional Medical Center and Southwest Community College sustained EF2 damage with the worst occurring to the Green Hills Education Center. The tornado continued tracking northeast and damaged a few farmsteads northeast of Creston.

3. Apr 8, 1999Tornado$2.0 million
   National Weather Service narrative

   As mentioned in the narrative above, an intense low pressure formed to the southwest of Iowa. The low tracked northeast and lifted into eastern Nebraska. Ahead of the low, a strong low level jet of around 60 knots continued through the day. A nearly stationary frontal boundary extended east from the low. It lifted into southeast Nebraska during the day, but made little progress into southern Iowa. Lines of thunderstorms formed along the boundary through the day and lifted north rapidly. These storms were elevated in nature and as a result produced most of their severe weather in the form of hail. As the day unfolded, a sharp dry line was clearly evident on the satellite as early…

4. May 6, 2007Hail$750,000
   National Weather Service narrative

   A very strong upper level low pressure trough had carved out over the western U.S. Iowa was in the strong southwest flow on the front side of this system. A surface warm front lifted north into southwest Iowa during the evening of the 5th. The airmass became quite unstable with plenty of deep moisture advection into the areas. Precipitable water values were in the 1.5 to 1.75 inch range by midnight. The lifted index fell to the -6 to -8 C. There was a reasonable amount of CAPE available with about 2500 J/kg at the onset of the event. The LCL was around 1000 meters and the freezing level was a relatively high 13,500 feet. With the warm front in the vicinity, there was a…

5. Oct 26, 1997Heavy Snow, Union$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. Apr 26, 2024Tornado$500,000
   National Weather Service narrative

   This tornado formed between the BNSF railroad and Highway 34 west of Afton and took a track very similar to a tornado which occurred earlier in the hour. It produced EF2 damage to several house on either side of Highway 34 as it travelled to the northeast. The tornado crossed Three Mile Lake just upstream of the dam and impacted a structure in the Wildlife Management Building area just a few hundred yards from the one impacted in the earlier tornado. This tornado then moved northeast through rural Union County impacting another farmstead producing EF2 damage. The tornado dissipated in the north central portion of Union County near the intersection of Pheasant Avenue and 130th Street.

7. Aug 9, 2009Thunderstorm Wind$500,000
   National Weather Service narrative

   A two-story brick building with wooden roof and shingles was damaged. Roof and shingles were blown off. A 4 foot diameter tree was uprooted in the city park and 3 air handling units were blown off of the East Union High School in Afton. Tin was blown off the feed mill.

8. Nov 10, 1998High Wind, Union$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. Apr 26, 2024Tornado$300,000
   National Weather Service narrative

   This tornado entered Union County from Adams County south of Cromwell. The tornado moved northeast through western Union county remaining in mostly rural locations. It did impact a few farmsteads along the way with mostly tree and outbuilding damage. The tornado moved into the far northwest portions of Creston producing EF2 damage to a multiple story townhouse along with taking down several trees. The tornado weakened quickly after this point with some minor damage observed at the atletic fields of the high school. The tornado then moved into open farmland north of Creston before dissipating.

10. Sep 19, 2010Flash Flood$250,000
    National Weather Service narrative

    Numerous roads flooded from Creston west to the county line. Rainfall reported of 4 to 6 inches.

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°FJul 5, 1911

All-time low

−34°FJan 12, 1912

Warmest night

84°FJul 7, 1980

Coldest day

−15°F3 times, most recently Dec 24, 1983

Wettest day

8.00 inSep 15, 1992

Snowiest day

12.0 in3 times, most recently Jan 4, 1971

Hottest year

1921mean 53.5°F

Coldest year

1893mean 46.8°F

Wettest year

201456.01 in

Driest year

196618.15 in

Snowiest season

61.0 in1911-12

Station Greenfield (USC00133438), 1,316 ft elevation, 17.8 miles from the population centre. Daily records from 1893 to October 27, 2026; 98.3% 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 USC00133438.
• 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.