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Weather & Climate in Mason, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Mason enjoys a temperate climate with an average annual temperature of 56°F (13°C). Winters average 32°F in January while summers reach 77°F in July. The area gets 293 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 46.4 inches (wetter than the 38-inch national average). The area receives 8.3 inches of snow annually. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 587 feet.
Temperature
32°F Jan (-0°C)
77°F Jul (25°C)
| Annual Average | 56.1°F |
| 4% above US avg | |
| January Average | 32°F (-0°C) |
| July Average | 77°F (25°C) |
| Sunny Days | 293 days/yr |
Geography
| Elevation | 587 ft (179 m) |
| Area | 1.3 sq mi (3.3 km²) |
| Population Density | 283/sq mi |
| Coordinates | 38.9543°N, 88.6271°W |
| Timezone | America/Chicago |
| County | Clay County County |
| Nearest Airport | Lawrenceville-Vincennes International (LWV) 57 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 41.1 / 100 |
| Social Vulnerability | 52.0 / 100 |
| Community Resilience | 88.1 / 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 | Relatively Low |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Low |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
55 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M5.2.
| Apr 18, 2008 | 7 km NNE of Bellmont, Illinois | M5.2 | 85 km | 14 km |
| Apr 18, 2008 | 9 km NNE of Bellmont, Illinois | M4.7 | 86 km | 15 km |
| Jun 18, 2002 | 6 km SW of Parkers Settlement, Indiana | M4.6 | 130 km | 16 km |
| Apr 21, 2008 | 7 km NNE of Bellmont, Illinois | M4.0 | 86 km | 18 km |
| Dec 7, 2000 | 7 km W of Evansville, Indiana | M3.9 | 139 km | 5 km |
| Nov 11, 1991 | 3 km W of Flat Rock, Illinois | M3.8 | 80 km | 0 km |
| Sep 19, 2017 | 4 km N of Bellmont, Illinois | M3.8 | 86 km | 12 km |
| Apr 25, 2008 | 8 km NNE of Bellmont, Illinois | M3.7 | 86 km | 13 km |
| Nov 20, 2012 | 7 km N of Bellmont, Illinois | M3.6 | 84 km | 19 km |
| Jan 2, 2006 | 3 km NNE of Eldorado, Illinois | M3.6 | 125 km | 7 km |
| Jun 5, 2008 | 8 km WNW of Mount Carmel, Illinois | M3.4 | 88 km | 16 km |
| May 30, 2015 | 4 km ENE of Geff, Illinois | M3.4 | 60 km | 26 km |
| Mar 2, 1990 | 9 km NW of Vernon, Illinois | M3.4 | 48 km | 0 km |
| May 1, 2008 | 8 km NNE of Bellmont, Illinois | M3.3 | 87 km | 14 km |
| May 13, 2025 | 7 km SSW of Lerna, Illinois | M3.3 | 52 km | 10 km |
| May 2, 2003 | 10 km ENE of Thompsonville, Illinois | M3.2 | 110 km | 0 km |
| Oct 24, 1990 | 5 km ENE of Woodlawn, Illinois | M3.2 | 74 km | 1 km |
| Jan 29, 1993 | 7 km WNW of Brownstown, Illinois | M3.2 | 36 km | 5 km |
| Apr 6, 1994 | 2 km NE of Tamaroa, Illinois | M3.2 | 102 km | 15 km |
| Jul 1, 2017 | 9 km SSE of Mulberry Grove, Illinois | M3.1 | 53 km | 17 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
496 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 29 fatalities, 571 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Nov 17, 2013 | EF4 | 93 km | 10.6 mi | 2 |
| Jun 2, 1990 | EF4 | 45 km | 23.0 mi | 0 |
| Jun 2, 1990 | EF4 | 31 km | 12.5 mi | 0 |
| Jun 2, 1990 | EF4 | 80 km | 106.0 mi | 1 |
| Jan 7, 1989 | EF4 | 91 km | 19.0 mi | 0 |
| Mar 20, 1976 | EF4 | 95 km | 63.7 mi | 0 |
| Dec 18, 1957 | EF4 | 85 km | 16.8 mi | 1 |
| Mar 31, 2023 | EF3 | 49 km | 40.9 mi | 6 |
| Dec 1, 2018 | EF3 | 84 km | 12.5 mi | 0 |
| Apr 21, 2002 | EF3 | 68 km | 31.5 mi | 1 |
| Jun 1, 1999 | EF3 | 99 km | 10.0 mi | 1 |
| Apr 19, 1996 | EF3 | 90 km | 17.0 mi | 0 |
| Aug 21, 1977 | EF3 | 53 km | 26.9 mi | 6 |
| Jul 28, 1976 | EF3 | 91 km | 0.1 mi | 0 |
| Aug 10, 1974 | EF3 | 77 km | 0.1 mi | 0 |
| Aug 10, 1974 | EF3 | 30 km | 0.1 mi | 0 |
| Apr 3, 1974 | EF3 | 96 km | 20.9 mi | 1 |
| Apr 1, 1974 | EF3 | 82 km | 3.3 mi | 0 |
| Apr 22, 1963 | EF3 | 99 km | 38.6 mi | 0 |
| Mar 6, 1961 | EF3 | 18 km | 21.2 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 32°F (-0°C) | 2.1 in | Coldest, Driest |
| February | 32°F (0°C) | 2.3 in | |
| March | 43°F (6°C) | 3.9 in | |
| April | 54°F (12°C) | 3.8 in | |
| May | 64°F (18°C) | 4.2 in | Wettest |
| June | 73°F (23°C) | 4.1 in | |
| July | 77°F (25°C) | 4.0 in | Warmest |
| August | 75°F (24°C) | 3.1 in | |
| September | 68°F (20°C) | 3.1 in | |
| October | 56°F (13°C) | 2.8 in | |
| November | 44°F (7°C) | 3.7 in | |
| December | 33°F (1°C) | 3.5 in |
Mason has a seasonal temperature swing of 45°F / from 32°F in January to 77°F in July. Total annual precipitation is 40.5 inches, with May being the wettest month (4.2") and January the driest (2.1").