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Weather & Climate in Mendon, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Mendon experiences four distinct seasons with an average annual temperature of 52°F (11°C). Winters average 25°F in January while summers reach 76°F in July. The area gets 282 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 764 feet.
Temperature
25°F Jan (-4°C)
76°F Jul (24°C)
| Annual Average | 52.0°F |
| 4% below US avg | |
| January Average | 25°F (-4°C) |
| July Average | 76°F (24°C) |
| Sunny Days | 282 days/yr |
Geography
| Elevation | 764 ft (233 m) |
| Area | 0.9 sq mi (2.2 km²) |
| Population Density | 1,315/sq mi |
| Coordinates | 40.0892°N, 91.2858°W |
| Timezone | America/Chicago |
| County | Hancock County County |
| Nearest Airport | Quincy Regional-Baldwin Field (UIN) 11 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 31.1 / 100 |
| Social Vulnerability | 64.8 / 100 |
| Community Resilience | 61.4 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Relatively Low |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Moderate |
| Winter Weather | Relatively Low |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Moderate |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
2 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M2.9.
| Feb 8, 2004 | 6 km SSW of Stoutsville, Missouri | M2.9 | 84 km | 5 km |
| Sep 19, 2024 | 1 km S of Old Monroe, Missouri | M2.6 | 138 km | 2 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
430 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 10 fatalities, 275 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 13, 1995 | EF4 | 55 km | 50.0 mi | 0 |
| May 13, 1995 | EF4 | 89 km | 7.0 mi | 0 |
| Apr 4, 2023 | EF3 | 86 km | 19.9 mi | 0 |
| May 27, 2019 | EF3 | 88 km | 7.3 mi | 0 |
| May 10, 2003 | EF3 | 60 km | 12.0 mi | 0 |
| Apr 8, 1999 | EF3 | 32 km | 7.5 mi | 0 |
| Jun 21, 1981 | EF3 | 58 km | 8.8 mi | 1 |
| Jul 23, 1975 | EF3 | 96 km | 11.1 mi | 0 |
| Apr 13, 1974 | EF3 | 86 km | 0.1 mi | 0 |
| Apr 13, 1974 | EF3 | 26 km | 11.0 mi | 0 |
| Sep 30, 1973 | EF3 | 34 km | 0.1 mi | 0 |
| May 1, 1973 | EF3 | 53 km | 3.6 mi | 2 |
| Apr 20, 1973 | EF3 | 75 km | 9.5 mi | 0 |
| Apr 16, 1967 | EF3 | 97 km | 19.4 mi | 2 |
| Jan 24, 1967 | EF3 | 91 km | 5.1 mi | 1 |
| Jan 24, 1967 | EF3 | 65 km | 4.3 mi | 1 |
| Aug 25, 1965 | EF3 | 87 km | 3.0 mi | 0 |
| Apr 21, 1964 | EF3 | 60 km | 14.1 mi | 0 |
| May 14, 1961 | EF3 | 41 km | 127.1 mi | 0 |
| Apr 24, 1961 | EF3 | 45 km | 64.2 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 25°F (-4°C) | 1.4 in | Coldest, Driest |
| February | 30°F (-1°C) | 1.4 in | |
| March | 41°F (5°C) | 3.0 in | |
| April | 53°F (12°C) | 3.7 in | |
| May | 63°F (17°C) | 4.5 in | |
| June | 72°F (22°C) | 3.8 in | |
| July | 76°F (24°C) | 4.6 in | Warmest, Wettest |
| August | 74°F (23°C) | 3.6 in | |
| September | 66°F (19°C) | 4.4 in | |
| October | 55°F (13°C) | 3.2 in | |
| November | 41°F (5°C) | 2.8 in | |
| December | 30°F (-1°C) | 2.2 in |
Mendon has a seasonal temperature swing of 51°F / from 25°F in January to 76°F in July. Total annual precipitation is 38.7 inches, with July being the wettest month (4.6") and January the driest (1.4").