Illinois City, IL
Full City Profile · Illinois · Mercer County County
5.0
/5.0
A+
Excellent
18
Population
39/sq mi density
50°F
Avg Temperature
A+
Overall
5.0 / 5.0
Strong
A+
Education
5.0 / 5.0
0.0% bachelor's degree or higher
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 75°F in July. Annual precipitation totals 36.4 inches. The area receives 23.5 inches of snow annually.
Temperature
22°F Jan (-6°C)
75°F Jul (24°C)
| Annual Average | 50.4°F |
| 7% below US avg | |
| January Average | 22°F (-6°C) |
| July Average | 75°F (24°C) |
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
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)
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 22°F (-6°C) | 1.2 in | Coldest, Driest |
| February | 26°F (-3°C) | 1.6 in | |
| March | 39°F (4°C) | 2.3 in | |
| April | 50°F (10°C) | 3.5 in | |
| May | 62°F (17°C) | 4.8 in | |
| June | 71°F (22°C) | 5.0 in | Wettest |
| July | 75°F (24°C) | 4.0 in | Warmest |
| August | 73°F (23°C) | 3.9 in | |
| September | 66°F (19°C) | 3.6 in | |
| October | 54°F (12°C) | 2.8 in | |
| November | 40°F (4°C) | 2.1 in | |
| December | 28°F (-2°C) | 1.7 in |
Illinois City has a seasonal temperature swing of 53°F / from 22°F in January to 75°F in July. Total annual precipitation is 36.4 inches, with June being the wettest month (5.0") and January the driest (1.2").