Williamson, IL
Full City Profile · Illinois · Madison County County
3.4
/5.0
B
Good
164
Population
140/sq mi density
$56,667
Median Income
$32,270 per capita
$75,500
Home Value
$100,968 Zillow
$779
Median Rent
14.2% income on rent
56°F
Avg Temperature
B
Overall
3.4 / 5.0
Good overall score based on economy, affordability, safety and education
B+
Economy
3.9 / 5.0
$56,667 median income, 0.0% unemployment
A+
Affordability
5.0 / 5.0
$75,500 home value, $779/mo rent
F
Education
1.2 / 5.0
2.9% bachelor's degree or higher
Williamson enjoys a temperate climate with an average annual temperature of 56°F (13°C). Winters average 30°F in January while summers reach 78°F in July. Annual precipitation totals 42.0 inches. The area receives 13.9 inches of snow annually. Air quality is rated Good with a median AQI of 49.
Temperature
30°F Jan (-1°C)
78°F Jul (25°C)
| Annual Average | 55.5°F |
| 3% above US avg | |
| January Average | 30°F (-1°C) |
| July Average | 78°F (25°C) |
Geography
| Elevation | 599 ft (183 m) |
| Area | 0.6 sq mi (1.6 km²) |
| Population Density | 140/sq mi |
| Coordinates | 38.9845°N, 89.7625°W |
| Timezone | America/Chicago |
| County | Madison County County |
| Nearest Airport | St Louis Regional (ALN) 17 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 49.0 |
| Rating | Good |
| Good Days % | 52.7% |
| Unhealthy Days | 6 |
Air Pollutants (EPA 2023)
| Ozone (O₃) | 0.0502 ppm |
| SO₂ (Sulfur Dioxide) | 1.30 ppb |
| PM2.5 (Fine Particles) | 9.6 μg/m³ |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 93.4 / 100 |
| Social Vulnerability | 25.9 / 100 |
| Community Resilience | 86.2 / 100 |
Hazard Breakdown
| Tornado | Relatively High |
| Hurricane | Very Low |
| Earthquake | Relatively Moderate |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively High |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively High |
| Winter Weather | Relatively High |
| Lightning | Relatively High |
| Ice Storm | Relatively Moderate |
| Drought | Relatively Low |
| Cold Wave | Relatively High |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 30°F (-1°C) | 2.6 in | Coldest |
| February | 35°F (2°C) | 2.3 in | Driest |
| March | 45°F (7°C) | 3.2 in | |
| April | 56°F (13°C) | 4.7 in | |
| May | 66°F (19°C) | 4.9 in | Wettest |
| June | 75°F (24°C) | 4.1 in | |
| July | 78°F (25°C) | 4.2 in | Warmest |
| August | 76°F (24°C) | 3.5 in | |
| September | 69°F (21°C) | 3.3 in | |
| October | 58°F (14°C) | 3.2 in | |
| November | 45°F (7°C) | 3.5 in | |
| December | 35°F (1°C) | 2.6 in |
Williamson has a seasonal temperature swing of 48°F / from 30°F in January to 78°F in July. Total annual precipitation is 42.0 inches, with May being the wettest month (4.9") and February the driest (2.3").