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Weather & Climate in Mason City, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Mason City experiences four distinct seasons with an average annual temperature of 52°F (11°C). Winters average 25°F in January while summers reach 75°F in July. The area gets 275 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 39.3 inches. The area receives 12.9 inches of snow annually. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 578 feet.
Temperature
25°F Jan (-4°C)
75°F Jul (24°C)
| Annual Average | 51.7°F |
| 4% below US avg | |
| January Average | 25°F (-4°C) |
| July Average | 75°F (24°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 578 ft (176 m) |
| Area | 1.0 sq mi (2.6 km²) |
| Population Density | 2,073/sq mi |
| Coordinates | 40.2022°N, 89.6971°W |
| Timezone | America/Chicago |
| County | Mason County County |
| Nearest Airport | General Downing - Peoria International (PIA) 32 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 43.0 / 100 |
| Social Vulnerability | 52.9 / 100 |
| Community Resilience | 68.7 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Relatively Low |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Very Low |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Moderate |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
3 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.3.
| May 13, 2025 | 7 km SSW of Lerna, Illinois | M3.3 | 150 km | 10 km |
| Jan 29, 1993 | 7 km WNW of Brownstown, Illinois | M3.2 | 142 km | 5 km |
| Mar 15, 2025 | 6 km W of Dwight, Illinois | M2.6 | 141 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
782 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 19 fatalities, 811 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Nov 17, 2013 | EF4 | 48 km | 46.4 mi | 3 |
| Jul 13, 2004 | EF4 | 73 km | 9.6 mi | 0 |
| May 13, 1995 | EF4 | 54 km | 7.0 mi | 0 |
| May 5, 1977 | EF4 | 38 km | 7.3 mi | 0 |
| Jun 29, 1976 | EF4 | 67 km | 4.9 mi | 0 |
| Mar 20, 1976 | EF4 | 89 km | 63.7 mi | 0 |
| Jun 14, 1957 | EF4 | 50 km | 4.3 mi | 2 |
| Apr 4, 2023 | EF3 | 55 km | 19.9 mi | 0 |
| Dec 1, 2018 | EF3 | 91 km | 12.5 mi | 0 |
| Feb 28, 2017 | EF3 | 84 km | 17.8 mi | 0 |
| Apr 19, 2011 | EF3 | 85 km | 4.3 mi | 0 |
| Dec 31, 2010 | EF3 | 28 km | 3.6 mi | 0 |
| Aug 19, 2009 | EF3 | 30 km | 24.3 mi | 0 |
| May 10, 2003 | EF3 | 30 km | 17.5 mi | 0 |
| Jun 1, 1999 | EF3 | 98 km | 10.0 mi | 1 |
| Apr 19, 1996 | EF3 | 61 km | 14.5 mi | 0 |
| Apr 19, 1996 | EF3 | 32 km | 9.4 mi | 0 |
| May 13, 1995 | EF3 | 31 km | 25.0 mi | 0 |
| May 9, 1995 | EF3 | 36 km | 50.0 mi | 0 |
| Jun 21, 1981 | EF3 | 79 km | 8.8 mi | 1 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 25°F (-4°C) | 1.5 in | Coldest, Driest |
| February | 29°F (-2°C) | 1.5 in | |
| March | 41°F (5°C) | 3.0 in | |
| April | 53°F (11°C) | 3.5 in | |
| May | 63°F (17°C) | 4.0 in | Wettest |
| June | 72°F (22°C) | 3.7 in | |
| July | 75°F (24°C) | 3.8 in | Warmest |
| August | 74°F (23°C) | 3.4 in | |
| September | 67°F (19°C) | 3.5 in | |
| October | 55°F (13°C) | 2.8 in | |
| November | 41°F (5°C) | 2.8 in | |
| December | 30°F (-1°C) | 2.6 in |
Mason City has a seasonal temperature swing of 50°F / from 25°F in January to 75°F in July. Total annual precipitation is 36.2 inches, with May being the wettest month (4.0") and January the driest (1.5").