Mason County, Illinois

What hazards hit Mason County most?

The most frequent records are severe thunderstorm wind events: 153 since 1964. 50% of its severe thunderstorm wind events since 1964 fell in May and June. The rank column places the county among Illinois's counties by days with a record per 1,000 square miles of land over each hazard's complete period.

Source: NOAA NCEI Storm Events Database (county and forecast-zone records attributed to the county; a zone record shows its own totals on each county it covers). Days: dates with at least one record of the hazard in the county. Ranks: days with a record per 1,000 square miles of land (Census Bureau 2024 Gazetteer), since 1950 for tornadoes, 1955 for hail and thunderstorm wind, 1996 for the rest.

How many tornadoes has Mason County had?

NOAA records 42 tornadoes in Mason County from 1951 to 2026, the strongest rated F3, with 1 death and 35 injuries recorded in the county. That is 26th of 102 Illinois counties by days with tornadoes per 1,000 square miles since 1950. A tornado that crossed a county line is counted in each county it touched, with the length of its path inside the county.

Counted as whole tornadoes rather than county records, the Storm Prediction Center's database holds 41 tornadoes whose track touched Mason County since 1950 (NOAA's county records number 42: they file a crossing tornado once per county segment, and the two databases differ on some tracks); along their whole tracks they killed 1 person.

Map of the strongest tornado tracks in Illinois.

Source: NOAA NCEI Storm Events Database, tornado records by county (path length in the county, maximum width); ratings as published: F scale before February 1, 2007, EF scale after. Whole-track figures: NOAA Storm Prediction Center tornado database (1950-2025). SPC severe weather database.

When was the last damaging storm in Mason County?

The most recent record with damage, injuries or deaths is the March 23, 2021 tornado ($27,000 in damage in 2025 dollars).

A tornado touched down at 10:28 PM CDT 3 miles northwest of Mason City. The tornado tracked northeastward, snapping 3 power poles along County Road 1250 North near the intersection with County Road 3300 East before dissipating at 10:34 PM CDT near the intersection of County Road 1400 North and County Road 3400 East.
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 950586)

Source: NOAA NCEI Storm Events Database; every record of 2025-2026 is listed, earlier ones when they caused deaths, injuries or $250,000 of damage (2025 dollars), and every tornado.

The deadliest and costliest records

A damage figure marked "step" is a record from before 1993: NOAA then filed damage by category, and the figure is the category as entered, in the dollars of that year, not an estimate of the loss.

Source: NOAA NCEI Storm Events Database: deaths and injuries direct and indirect; damage is property plus crops as estimated by the National Weather Service, converted to 2025 dollars.

Is it getting more frequent?

Records per decade for Mason County's most frequent hazards. Counts rose everywhere after 1996, when NOAA began recording every event type, so compare decades within a hazard's complete period only (the shaded cells come before it).

Source: NOAA NCEI Storm Events Database, records per calendar decade; zone records from the CZ_TYPE field (Z).

What time of year?

50% of its severe thunderstorm wind events since 1964 fell in May and June. The two busiest months are in violet.

Source: NOAA NCEI Storm Events Database, records by the month they began.

Federal disaster declarations for Mason County

FEMA's register lists 18 declarations that include Mason County: 14 major disasters, 4 emergencies and 0 fire management assistance declarations. Most were for flood (6) and severe storm (4).

Source: FEMA OpenFEMA Disaster Declarations Summaries (v2), declarations through October 2, 2026; one declaration is counted once however many areas it names. OpenFEMA dataset page.

How many floods has Mason County had?

NOAA's Storm Events Database holds 28 flood or flash flood records for Mason County from 1997 to 2023, on 26 days, with 1 death. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Mason County ranks 553rd of 2,942 U.S. counties.

The National Flood Insurance Program has paid $3.4 million on 452 claims filed in Mason County; the most in one year was 147 in 1993. Claims count insured losses only: uninsured flood damage is not in this file.

Source: FEMA OpenFEMA NFIP Redacted Claims, as of September 8, 2026; claims by year of loss, payments in the dollars of the year paid. OpenFEMA dataset page.

FEMA's modeled risk for Mason County

FEMA's National Risk Index rates Mason County Relatively Low overall, with an expected annual loss of $12.3 million. These are FEMA's model estimates of future loss from 18 hazards, not a count of what happened; they can differ from the record above.

Source: FEMA National Risk Index, county table, December 2025 release. FEMA's National Risk Index map.

Counties that share a border with Mason County

1. Tazewell County 913
2. Fulton County 758
3. Logan County 684
4. Mason County 384
5. Menard County 367
6. Schuyler County 326
7. Cass County 319

Source: U.S. Census Bureau county adjacency file; NOAA NCEI Storm Events Database, records since 1950. The Census Bureau's adjacency file.

Next

• Tornadoes in IllinoisEvery Illinois tornado since 1950 and the counties with the most per square mile
• Severe thunderstorm wind in IllinoisThe state's severe thunderstorm wind events, by county, year and month
• The Illinois recordEvery hazard in the state, its deadliest events and its federal declarations
• FEMA's risk rating for each hazard in Mason CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download Mason County's FEMA declarations (CSV)18 rows: every declaration that named the county, for your own analysis