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Seneca, IL
Full City Profile · Illinois · Grundy County County
3.1
/5.0
B
Good
2,525
Population
407/sq mi density
$91,065
Median Income
$42,714 per capita
$206,400
Home Value
$246,823 Zillow
$988
Median Rent
21.3% income on rent
50°F
Avg Temperature
275 sunny days/yr
649
Violent Crime/100K
2,509 property/100K
B
Overall
3.1 / 5.0
Good overall score based on economy, affordability, safety and education
A+
Economy
4.5 / 5.0
$91,065 median income, 2.5% unemployment
A+
Affordability
5.0 / 5.0
$206,400 home value, $988/mo rent
F
Safety
1.0 / 5.0
649 violent crimes/100K (71% above avg)
C
Education
2.0 / 5.0
12.9% bachelor's degree or higher
Seneca experiences four distinct seasons with an average annual temperature of 50°F (10°C). Winters average 23°F in January while summers reach 73°F in July. The area gets 275 sunny days per year. Annual precipitation totals 39.0 inches. The area receives 25.0 inches of snow annually. Air quality is rated Good with a median AQI of 43.
Temperature
23°F Jan (-5°C)
73°F Jul (23°C)
| Annual Average | 49.7°F |
| 8% below US avg | |
| January Average | 23°F (-5°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 508 ft (155 m) |
| Area | 2.7 sq mi (7.0 km²) |
| Population Density | 407/sq mi |
| Coordinates | 41.3026°N, 88.6147°W |
| Timezone | America/Chicago |
| County | Grundy County County |
| Nearest Airport | Joliet Regional (JOT) 27 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 66.5 / 100 |
| Social Vulnerability | 10.6 / 100 |
| Community Resilience | 99.5 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Very Low |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Very Low |
| Ice Storm | Very Low |
| Drought | Relatively Low |
| Cold Wave | Relatively High |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 23°F (-5°C) | 1.5 in | Coldest |
| February | 27°F (-3°C) | 1.4 in | Driest |
| March | 38°F (3°C) | 2.7 in | |
| April | 50°F (10°C) | 3.7 in | |
| May | 61°F (16°C) | 3.9 in | |
| June | 70°F (21°C) | 3.9 in | Wettest |
| July | 73°F (23°C) | 3.9 in | Warmest |
| August | 72°F (22°C) | 3.5 in | |
| September | 65°F (18°C) | 3.6 in | |
| October | 53°F (12°C) | 2.6 in | |
| November | 40°F (5°C) | 2.9 in | |
| December | 28°F (-2°C) | 2.4 in |
Seneca has a seasonal temperature swing of 50°F / from 23°F in January to 73°F in July. Total annual precipitation is 36.0 inches, with June being the wettest month (3.9") and February the driest (1.4").