Mason City

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond this area.
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.

Flood insurance figures are for Cerro Gordo County, the county that contains Mason City.

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 in Cerro Gordo County, the county that contains Mason City.

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.

The drought index is for Cerro Gordo County, the county that contains Mason City.

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, Cerro Gordo$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 7, 2008Flood$1.0 million
   National Weather Service narrative

   Heavy rain fell once again across a large part of Iowa, especially across the north and northeast. This rain fell on rivers that were already close to flood stage as they were just beginning to fall after the flooding from earlier in the month. The rainfall of the first week of June set the state for what would become record flooding over a large part of the northeast half of Iowa, even eclipsing the records set just 15 years previous in 1993. Damage became widespread, both to property and infrastructure as well as agriculturally. More details of the record rains will be included with the next event, which occurred just a couple days later.

3. Jul 19, 1999Flash Flood$1.0 million
   National Weather Service narrative

   A nearly stationary frontal boundary was draped across Iowa during the afternoon of the 18th into the night. Thunderstorms erupted in the vicinity of the front as dew point temperatures in the mid 70s to around 80 pooled just south of front. Most of the storms produced heavy rain and gusty winds with very few producing severe weather. Two distinct mesoscale convective systems moved across northern Iowa. The first one produced some wind damage as it moved across. Trees were downed in Kossuth County southeast of Irvington. Another cell ripped shingles from a home in Dumont in Butler County. The main problem was flash flooding over north central Iowa. Near Manly in Worth County. 5.75…

4. Aug 23, 2014Flash Flood$500,000
   National Weather Service narrative

   The roof of a Walmart collapsed form water weight. Water was deep enough to reach the roof on cars with several submerged along Highways 65 and 122. Several roads were impassable in the city until around 0820 CST.

5. Dec 23, 2009Ice Storm, Cerro Gordo$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…

6. Jun 8, 2008Flash Flood$500,000
   National Weather Service narrative

   The levee failed along North Hampshire Avenue in Mason City. A subdivision near the river is flooding.

7. Nov 10, 1998High Wind, Cerro Gordo$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…

8. Aug 19, 2007Flash Flood$250,000
   National Weather Service narrative

   Heavy rains caused flooding with 1 to 2 feet of water in the streets. Evacuations were necessary in East Park.

9. Jun 23, 1998Thunderstorm Wind$250,000
   National Weather Service narrative

   Once again, a warm frontal boundary was located to the south of Iowa with very warm and unstable air just to the south of the front. Dew point temperatures were in the low 70s in the warm air. This moisture was drawn north over the frontal boundary, into Iowa. A large mesoscale convective system developed over northwest Iowa and moved east during the evening hours. Initially, the system produced hail over an inch in diameter, but the main severe weather associated with the storms was high winds. Some building damage was reported in Palmer in Pocahontas County. A grain bin was damaged by high winds in Humboldt in Humboldt County. Windows were blown out at a mall department store in…

10. Feb 24, 2007Winter Storm, Cerro Gordo$250,000
    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…

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

104°FJul 7, 1980

All-time low

−32°FFeb 2, 1996

Warmest night

79°FJul 10, 1976

Coldest day

−20°FDec 23, 1983

Wettest day

6.33 inAug 22, 1954

Snowiest day

12.4 inMar 24, 2018

Hottest year

2012mean 49.9°F

Coldest year

1950mean 41.6°F

Wettest year

201850.01 in

Driest year

195814.79 in

Snowiest season

68.5 in1970-71

Station Mason City Municipal Airport (USW00014940), 1,188 ft elevation, 6.4 miles from the city centre. Daily records from 1948 to October 27, 2026; 99.9% 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.

Declarations for Cerro Gordo County.

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.

• 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 USW00014940.
• 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.