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Union Mill, VA
Full City Profile · Virginia · Manassas Park city County
3.9
/5.0
B+
Good
4,351
Population
436/sq mi density
$245,265
Median Income
$94,379 per capita
$942,400
Home Value
$994,825 Zillow
$2,581
Median Rent
51.0% income on rent
56°F
Avg Temperature
297 sunny days/yr
132
Violent Crime/100K
915 property/100K
B+
Overall
3.9 / 5.0
Good overall score based on economy, affordability, safety and education
A+
Economy
5.0 / 5.0
$245,265 median income, 1.0% unemployment
A+
Affordability
4.5 / 5.0
$942,400 home value, $2,581/mo rent
F
Safety
1.0 / 5.0
132 violent crimes/100K
A+
Education
5.0 / 5.0
73.7% bachelor's degree or higher
Union Mill enjoys a temperate climate with an average annual temperature of 56°F (13°C). Winters average 33°F in January while summers reach 78°F in July. The area gets 297 sunny days per year. Air quality is rated Good with a median AQI of 35.
Temperature
33°F Jan (1°C)
78°F Jul (26°C)
| Annual Average | 55.5°F |
| 3% above US avg | |
| January Average | 33°F (1°C) |
| July Average | 78°F (26°C) |
| Sunny Days | 297 days/yr |
Geography
| Elevation | 319 ft (97 m) |
| Area | 10.1 sq mi (26.1 km²) |
| Population Density | 436/sq mi |
| Coordinates | 38.8013°N, 77.3871°W |
| Timezone | America/New_York |
| County | Manassas Park city County |
| Nearest Airport | Washington Dulles International (IAD) 9 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 35.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 4.9 / 100 |
| Social Vulnerability | 26.8 / 100 |
| Community Resilience | 12.0 / 100 |
Hazard Breakdown
| Tornado | Very Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Very Low |
| Strong Wind | Relatively Low |
| Heat Wave | Relatively Low |
| Winter Weather | Very Low |
| Lightning | Relatively Low |
| Ice Storm | Very Low |
| Drought | No Rating |
| Cold Wave | Very Low |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 33°F (1°C) | 2.9 in | Coldest |
| February | 37°F (3°C) | 2.6 in | Driest |
| March | 45°F (7°C) | 3.2 in | |
| April | 55°F (13°C) | 3.0 in | |
| May | 64°F (18°C) | 3.8 in | Wettest |
| June | 72°F (22°C) | 3.5 in | |
| July | 78°F (26°C) | 3.5 in | Warmest |
| August | 75°F (24°C) | 3.7 in | |
| September | 68°F (20°C) | 3.5 in | |
| October | 57°F (14°C) | 3.2 in | |
| November | 47°F (8°C) | 3.3 in | |
| December | 38°F (3°C) | 3.0 in |
Union Mill has a seasonal temperature swing of 45°F / from 33°F in January to 78°F in July. Total annual precipitation is 39.2 inches, with May being the wettest month (3.8") and February the driest (2.6").