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Weather & Climate in Illinois City, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Illinois City experiences four distinct seasons with an average annual temperature of 50°F (10°C). Winters average 22°F in January while summers reach 74°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 39.1 inches. The area receives 21.8 inches of snow annually, a moderate snowfall amount. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 767 feet.
Temperature
22°F Jan (-5°C)
74°F Jul (23°C)
| Annual Average | 50.0°F |
| 7% below US avg | |
| January Average | 22°F (-5°C) |
| July Average | 74°F (23°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 767 ft (234 m) |
| Area | 0.5 sq mi (1.2 km²) |
| Population Density | 39/sq mi |
| Coordinates | 41.3991°N, 90.8997°W |
| Timezone | America/Chicago |
| County | Mercer County County |
| Nearest Airport | Quad Cities International (MLI) 21 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 8.8 / 100 |
| Social Vulnerability | 10.6 / 100 |
| Community Resilience | 85.7 / 100 |
Hazard Breakdown
| Tornado | Very Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Very Low |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively Moderate |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Low |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
1 earthquake (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.5.
| Sep 2, 1999 | 8 km W of Amboy, Illinois | M3.5 | 127 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
649 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 7 fatalities, 275 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Mar 31, 2023 | EF4 | 95 km | 19.9 mi | 0 |
| May 13, 1995 | EF4 | 97 km | 50.0 mi | 0 |
| Mar 29, 1981 | EF4 | 85 km | 5.1 mi | 0 |
| Apr 11, 1965 | EF4 | 50 km | 91.5 mi | 1 |
| Jun 1, 2007 | EF3 | 28 km | 15.8 mi | 0 |
| May 15, 1998 | EF3 | 71 km | 47.0 mi | 0 |
| May 9, 1995 | EF3 | 20 km | 10.0 mi | 0 |
| May 9, 1995 | EF3 | 93 km | 22.0 mi | 0 |
| Jul 13, 1992 | EF3 | 89 km | 5.0 mi | 0 |
| Mar 13, 1990 | EF3 | 56 km | 15.5 mi | 0 |
| May 8, 1988 | EF3 | 40 km | 32.0 mi | 0 |
| Aug 15, 1978 | EF3 | 18 km | 6.4 mi | 0 |
| Jun 13, 1975 | EF3 | 97 km | 6.6 mi | 0 |
| Jun 20, 1974 | EF3 | 83 km | 10.6 mi | 1 |
| Jun 14, 1974 | EF3 | 19 km | 48.6 mi | 0 |
| May 13, 1974 | EF3 | 35 km | 3.6 mi | 0 |
| Apr 21, 1967 | EF3 | 97 km | 0.1 mi | 0 |
| Jan 24, 1967 | EF3 | 88 km | 4.3 mi | 1 |
| Apr 19, 1966 | EF3 | 35 km | 2.0 mi | 0 |
| Aug 25, 1965 | EF3 | 68 km | 3.0 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
5 wildfires (100+ acres) recorded within 100 km. Largest: UNIT 3 (1,206 acres, 1999).
| Year | Name | Acres Burned | Distance |
| 1999 | UNIT 3 | 1,206 | 36 km |
| 2002 | HSB 03 2 | 1,130 | 36 km |
| 2000 | DESTRUST A | 756 | 35 km |
| 2006 | HSB 003 | 674 | 36 km |
| 2004 | HSB 009 | 608 | 35 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 22°F (-5°C) | 1.3 in | Coldest |
| February | 27°F (-3°C) | 1.1 in | Driest |
| March | 38°F (3°C) | 2.6 in | |
| April | 50°F (10°C) | 3.5 in | |
| May | 61°F (16°C) | 3.9 in | |
| June | 71°F (21°C) | 4.2 in | |
| July | 74°F (23°C) | 4.3 in | Warmest, Wettest |
| August | 73°F (23°C) | 4.0 in | |
| September | 65°F (18°C) | 3.8 in | |
| October | 53°F (12°C) | 2.8 in | |
| November | 39°F (4°C) | 2.3 in | |
| December | 26°F (-3°C) | 1.9 in |
Illinois City has a seasonal temperature swing of 52°F / from 22°F in January to 74°F in July. Total annual precipitation is 35.8 inches, with July being the wettest month (4.3") and February the driest (1.1").