Calhoun County

Every recorded tornado

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

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, Calhoun$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. Jul 14, 2021Tornado$2.5 million
   National Weather Service narrative

   This was the first and strongest tornado of the day. It developed west southwest of Lake City and produced tree and power line damage. The tornado moved into and across the southern portion of Lake City. Imagery from UAV's and chasers show that the tornado was multi-vortex as it passed through the city. Up to EF2 damage occurred as it passed through town. As the tornado moved east of the town, it began to consolidate into a larger funnel and strengthen. It passed through a farmstead producing considerable damage to the farmhouse and out buildings with EF3 damage noted on the house. The tornado continued for a few more miles and impacted a confinement facility before lifting to the…

3. May 30, 1998Hail$1.0 million
   National Weather Service narrative

   A very unstable airmass was over Iowa. In spite of the instability, the atmosphere was capped by very warm air aloft. Temperatures at the 700 mb level were between 12 degrees C and 14 degrees C. As a result, thunderstorms had a difficult time forming. The atmosphere was primed with CAPE values in the 4000 to 6000 J/kg range by late morning. Helicity values were near 300 M2/S2. One cell was able to break the cap and became severe. It was a prolific hail producer as well as spawning several tornadoes. Hail reports indicated frequent baseball size hail with a few reports to softball size and larger. The largest report was an incredible 5 inch diameter stone north of Gilbert in Story…

4. May 10, 2015Tornado$1.0 million
   National Weather Service narrative

   Tornado moved from Carroll County into Calhoun County. It moved across the western side of Lake City, doing EF1 damage to houses and the high school. It remained in rural areas of Calhoun County for the remainder of it's path, broadening as it went along. The tornado lifted shortly before crossing Highway 20.

5. May 30, 1998Hail$750,000
   National Weather Service narrative

   A very unstable airmass was over Iowa. In spite of the instability, the atmosphere was capped by very warm air aloft. Temperatures at the 700 mb level were between 12 degrees C and 14 degrees C. As a result, thunderstorms had a difficult time forming. The atmosphere was primed with CAPE values in the 4000 to 6000 J/kg range by late morning. Helicity values were near 300 M2/S2. One cell was able to break the cap and became severe. It was a prolific hail producer as well as spawning several tornadoes. Hail reports indicated frequent baseball size hail with a few reports to softball size and larger. The largest report was an incredible 5 inch diameter stone north of Gilbert in Story…

6. Jan 20, 2010Ice Storm, Calhoun$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…

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

   A trained spotter reports extensive tree, window, roof, and crop damage fro high winds and large hail around somers.

8. Jun 30, 2014Hail$500,000
   National Weather Service narrative

   A very dynamic pattern was in place over the state with a closed low located over southern Canada into the north central U.S. A very strong jet of 85 to 100 kts as present at 250 mb. CAPE by early morning was already 3000 to 4000 J/kg with downdraft CAPE of 1000 to 1400 J/kg. CAPE in the -10 to -30 C layer of the atmosphere was between 1000 and 1400 J/kg. The freezing level was around 14,000 feet with precipitable water values near 2 inches. The LCL remained around 750 meters with 75 J/kg of CAPE in the 0-3 km layer. There was strong shear present, with 60-80 kts of effective shear. A cold front moved into Iowa during the day and moved across the state. This event was similar to…

9. Dec 23, 2009Ice Storm, Calhoun$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. Nov 10, 1998High Wind, Calhoun$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…

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

110°FAug 18, 1936

All-time low

−35°F3 times, most recently Jan 31, 2019

Warmest night

82°FJun 15, 1987

Coldest day

−16°FFeb 2, 1905

Wettest day

6.06 inJul 23, 1979

Snowiest day

14.0 in3 times, most recently Mar 8, 1961

Hottest year

1931mean 52.5°F

Coldest year

1996mean 43.6°F

Wettest year

190849.98 in

Driest year

189417.34 in

Snowiest season

66.9 in1961-62

Station Rockwell City (USC00137161), 1,214 ft elevation, 0.3 miles from the population centre. Daily records from 1894 to August 31, 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 USC00137161.
• 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.