Dorchester, IL
Full City Profile · Illinois · Macoupin County County
4.0
/5.0
A
Great
185
Population
257/sq mi density
$121,250
Median Income
$40,152 per capita
$133,300
Home Value
$171,282 Zillow
53°F
Avg Temperature
A
Overall
4.0 / 5.0
Strong
A+
Economy
5.0 / 5.0
$121,250 median income, 0.0% unemployment
A+
Affordability
5.0 / 5.0
$133,300 home value, /mo rent
C
Education
2.0 / 5.0
12.5% bachelor's degree or higher
Dorchester experiences four distinct seasons with an average annual temperature of 53°F (12°C). Winters average 28°F in January while summers reach 76°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 35.
Temperature
28°F Jan (-2°C)
76°F Jul (25°C)
| Annual Average | 53.4°F |
| 1% below US avg | |
| January Average | 28°F (-2°C) |
| July Average | 76°F (25°C) |
Geography
| Elevation | 655 ft (200 m) |
| Area | 0.3 sq mi (0.7 km²) |
| Population Density | 257/sq mi |
| Coordinates | 39.0859°N, 89.8877°W |
| Timezone | America/Chicago |
| County | Macoupin County County |
| Nearest Airport | St Louis Regional (ALN) 16 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 35.0 |
| Rating | Good |
| Good Days % | 93.4% |
| Unhealthy Days | 1 |
Air Pollutants (EPA 2023)
| Ozone (O₃) | 0.0477 ppm |
| NO₂ (Nitrogen Dioxide) | 3.9 ppb |
| SO₂ (Sulfur Dioxide) | 0.61 ppb |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 79.9 / 100 |
| Social Vulnerability | 50.7 / 100 |
| Community Resilience | 72.7 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Hurricane | Very Low |
| Earthquake | Relatively Moderate |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Relatively Moderate |
| Strong Wind | Relatively High |
| Heat Wave | Relatively Moderate |
| Winter Weather | Relatively Moderate |
| Lightning | Relatively High |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Moderate |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 28°F (-2°C) | 2.6 in | Coldest |
| February | 32°F (0°C) | 2.3 in | Driest |
| March | 42°F (6°C) | 3.2 in | |
| April | 54°F (12°C) | 4.7 in | |
| May | 64°F (18°C) | 4.9 in | Wettest |
| June | 73°F (23°C) | 4.1 in | |
| July | 76°F (25°C) | 4.2 in | Warmest |
| August | 74°F (24°C) | 3.5 in | |
| September | 67°F (20°C) | 3.3 in | |
| October | 55°F (13°C) | 3.2 in | |
| November | 43°F (6°C) | 3.5 in | |
| December | 33°F (0°C) | 2.6 in |
Dorchester has a seasonal temperature swing of 48°F / from 28°F in January to 76°F in July. Total annual precipitation is 42.0 inches, with May being the wettest month (4.9") and February the driest (2.3").