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Union, IL
Full City Profile · Illinois · McHenry County County
4.1
/5.0
A
Great
753
Population
896/sq mi density
$100,104
Median Income
$44,115 per capita
$224,600
Home Value
$413,839 Zillow
48°F
Avg Temperature
260 sunny days/yr
A
Overall
4.1 / 5.0
Strong
A+
Economy
4.9 / 5.0
$100,104 median income, 2.6% unemployment
A+
Affordability
5.0 / 5.0
$224,600 home value, /mo rent
C
Education
2.3 / 5.0
15.7% bachelor's degree or higher
Union experiences four distinct seasons with an average annual temperature of 48°F (9°C). Winters average 21°F in January while summers reach 73°F in July. The area gets 260 sunny days per year. Annual precipitation totals 37.6 inches. The area receives 30.8 inches of snow annually. Air quality is rated Good with a median AQI of 43.
Temperature
21°F Jan (-6°C)
73°F Jul (23°C)
| Annual Average | 48.2°F |
| 11% below US avg | |
| January Average | 21°F (-6°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 260 days/yr |
Geography
| Elevation | 857 ft (261 m) |
| Area | 0.8 sq mi (2.2 km²) |
| Population Density | 896/sq mi |
| Coordinates | 42.2316°N, 88.5448°W |
| Timezone | America/Chicago |
| County | McHenry County County |
| Nearest Airport | Chicago/Rockford International (RFD) 28 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Air Pollutants (EPA 2023)
| Ozone (O₃) | 0.0484 ppm |
| PM2.5 (Fine Particles) | 9.1 μg/m³ |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 90.8 / 100 |
| Social Vulnerability | 10.6 / 100 |
| Community Resilience | 84.0 / 100 |
Hazard Breakdown
| Tornado | Relatively High |
| Hurricane | Very Low |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively Moderate |
| Strong Wind | Relatively High |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Moderate |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively Low |
| Drought | Relatively Low |
| Cold Wave | Relatively High |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Tsunami History
1 tsunami recorded within 500 km. Highest wave on record: 3.0 m (10 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1954 | MICHIGAN CITY, IN (LAKE MICHIGAN) | Avalanche | 3.0 m | 7 | 150 km |
Source: NOAA/NCEI Historical Tsunami Database. Sorted by wave height.
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 21°F (-6°C) | 1.4 in | Coldest |
| February | 24°F (-4°C) | 1.2 in | Driest |
| March | 35°F (2°C) | 2.4 in | |
| April | 47°F (8°C) | 3.7 in | |
| May | 59°F (15°C) | 3.7 in | |
| June | 68°F (20°C) | 4.3 in | Wettest |
| July | 73°F (23°C) | 4.0 in | Warmest |
| August | 70°F (21°C) | 4.2 in | |
| September | 62°F (17°C) | 3.8 in | |
| October | 51°F (10°C) | 2.6 in | |
| November | 37°F (3°C) | 2.7 in | |
| December | 25°F (-4°C) | 2.0 in |
Union has a seasonal temperature swing of 52°F / from 21°F in January to 73°F in July. Total annual precipitation is 36.1 inches, with June being the wettest month (4.3") and February the driest (1.2").