Johnston, IA
Full City Profile · Iowa · Polk County County
4.0
/5.0
A
Great
24,196
Population
1,241/sq mi density
$103,430
Median Income
$56,641 per capita
$346,200
Home Value
$399,597 Zillow
$1,288
Median Rent
29.6% income on rent
50°F
Avg Temperature
77
Violent Crime/100K
757 property/100K
A
Overall
4.0 / 5.0
Strong
A+
Economy
5.0 / 5.0
$103,430 median income, 1.8% unemployment
A+
Affordability
4.8 / 5.0
$346,200 home value, $1,288/mo rent
F
Safety
1.0 / 5.0
77 violent crimes/100K
A+
Education
5.0 / 5.0
57.9% bachelor's degree or higher
Johnston experiences four distinct seasons with an average annual temperature of 50°F (10°C). Winters average 22°F in January while summers reach 75°F in July. Annual precipitation totals 36.2 inches. The area receives 38.0 inches of snow annually. Air quality is rated Good with a median AQI of 45.
Temperature
22°F Jan (-6°C)
75°F Jul (24°C)
| Annual Average | 50.3°F |
| 7% below US avg | |
| January Average | 22°F (-6°C) |
| July Average | 75°F (24°C) |
Geography
| Elevation | 833 ft (254 m) |
| Area | 18.3 sq mi (47.5 km²) |
| Population Density | 1,241/sq mi |
| Coordinates | 41.6920°N, 93.7245°W |
| Timezone | America/Chicago |
| County | Polk County County |
| Nearest Airport | Des Moines International (DSM) 13 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 45.0 |
| Rating | Good |
| Good Days % | 67.5% |
| Unhealthy Days | 0 |
Air Pollutants (EPA 2023)
| Ozone (O₃) | 0.0449 ppm |
| NO₂ (Nitrogen Dioxide) | 10.2 ppb |
| PM2.5 (Fine Particles) | 9.4 μg/m³ |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 92.0 / 100 |
| Social Vulnerability | 17.0 / 100 |
| Community Resilience | 91.2 / 100 |
Hazard Breakdown
| Tornado | Relatively High |
| Hurricane | Very Low |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively High |
| Strong Wind | Very High |
| Heat Wave | Relatively High |
| Winter Weather | Relatively High |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively High |
| Drought | Relatively High |
| Cold Wave | Relatively High |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 22°F (-6°C) | 1.0 in | Coldest, Driest |
| February | 26°F (-3°C) | 1.3 in | |
| March | 39°F (4°C) | 2.2 in | |
| April | 51°F (10°C) | 4.0 in | |
| May | 62°F (17°C) | 4.8 in | |
| June | 72°F (22°C) | 5.4 in | Wettest |
| July | 75°F (24°C) | 4.3 in | Warmest |
| August | 73°F (23°C) | 4.0 in | |
| September | 66°F (19°C) | 3.4 in | |
| October | 53°F (12°C) | 2.5 in | |
| November | 39°F (4°C) | 2.0 in | |
| December | 27°F (-3°C) | 1.5 in |
Johnston has a seasonal temperature swing of 54°F / from 22°F in January to 75°F in July. Total annual precipitation is 36.2 inches, with June being the wettest month (5.4") and January the driest (1.0").