Cass County

Every recorded tornado

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

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.

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, Cass$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. Jun 14, 1998Flood, Cass$2.5 million
   National Weather Service narrative

   After a brief lull from the rain on the 12th, a large mesoscale convective system developed near the center of an upper level low pressure center over southwest Iowa during the early morning hours of the 14th. Extremely heavy rain fell over southwest and central Iowa from this storm. The rain gage at Atlantic had a 24 hour total rainfall of 13.18 inches. This established a new official record for the greatest amount of rainfall in a 24 hour period. Cass County was covered by a large area of 4 to 8 inch rains, which essentially submerged the entire county. The east Fork of the Nishnabotna at Atlantic 5 SW crested on the 15th at 22.36 feet, missing the all-time record set in…

3. Jun 14, 1998Flash Flood$2.0 million
   National Weather Service narrative

   A strong upper level system combined with a warm front located to the south of Iowa set the stage for a major flood event. Iowa soils were already saturated before the event took began. The severe thunderstorms mentioned above were only the beginning. They moved off to the northeast during the night as the upper level low pressure system became nearly stacked over southwest Iowa. A small cluster of thunderstorms formed over the southwest counties during the early morning hours. There was little movement and heavy rainfall ensued over Cass County. Cass County was the hardest hit as 13.18 inches of rain fell during the morning into early afternoon hours. Seven inches of it fell in a…

4. Jun 21, 1997Thunderstorm Wind$1.1 million
5. May 6, 2007Tornado$1.0 million
   National Weather Service narrative

   Tornado touched down on the southern Cass County line and moved northeast. The last 2 miles of the track showed an intermittent nature. Average path width was 100 to 200 yards wide with a maximum width of about one half mile. Estimated wind speed was 120 to 130 MPH.

6. May 6, 2007Flood$1.0 million
   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…

7. Jan 20, 2010Ice Storm, Cass$750,000
   National Weather Service narrative

   A strong push of warm air aloft took place over the central U.S. with 850 mb temperatures warming well above zero C over much of the state. During the day on the 19th a relatively strong high moved southeast to the east of Iowa. The easterly flow of cool air in the low levels established a strong inversion over the state. Surface temperatures fell into the teens and 20s in the cool easterly flow. A strong weather system from the southwest U.S. moved east across the southern half of the country during the night of the 19th into the daytime hours of the 20th. The low passed south of Iowa, however a strong push of warm and moist air moved into Iowa during the early morning of the…

8. Oct 26, 1997Heavy Snow, Cass$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…

9. Dec 23, 2009Ice Storm, Cass$500,000
   National Weather Service narrative

   Part 1 of 2: A major winter storm system affected the central U.S. during Christmas week. There were two upper level systems involved with this storm. The southern stream low dove into the southern U.S. and then turned northeast. The turn was sharper than is typical as the northern stream upper low pushed southeast. The southern stream and polar low interacted with each other, resulting in a Fuji Wara effect. The southern low turned north, then eventually northwest and moved from northern Louisiana into Iowa. This resulted in a considerable amount of warm air being drawn north over Iowa. Cold air remained in place at the surface due to an existing deep snow cover over most of the…

10. Jun 21, 1997Thunderstorm Wind$500,000

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

117°FJul 25, 1936

All-time low

−37°FJan 12, 1974

Warmest night

84°F2 times, most recently Aug 2, 1964

Coldest day

−16°FDec 24, 1983

Wettest day

13.18 inJun 14, 1998

Snowiest day

14.0 in2 times, most recently Dec 9, 2009

Hottest year

1921mean 54.5°F

Coldest year

2014mean 43.8°F

Wettest year

199855.96 in

Driest year

202018.82 in

Snowiest season

58.4 in1961-62

Station Atlantic 1 Ne (USC00130364), 1,152 ft elevation, 3.8 miles from the population centre. Daily records from 1893 to October 27, 2026; 98.1% 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 USC00130364.
• 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.