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Weather & Climate in Onslow, IA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Onslow experiences four distinct seasons with an average annual temperature of 48°F (9°C). Winters average 19°F in January while summers reach 73°F in July. The area gets 260 sunny days per year, above the national average. Annual precipitation totals 39.3 inches. The area receives 31.1 inches of snow annually, a moderate snowfall amount. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 926 feet.
Temperature
19°F Jan (-7°C)
73°F Jul (23°C)
| Annual Average | 47.9°F |
| 11% below US avg | |
| January Average | 19°F (-7°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 260 days/yr |
Geography
| Elevation | 926 ft (282 m) |
| Area | 0.2 sq mi (0.6 km²) |
| Population Density | 1,611/sq mi |
| Coordinates | 42.1069°N, 91.0151°W |
| Timezone | America/Chicago |
| County | Jones County County |
| Nearest Airport | Monticello Regional (MXO) 11 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 32.7 / 100 |
| Social Vulnerability | 10.6 / 100 |
| Community Resilience | 78.9 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Relatively Low |
| Strong Wind | Relatively Moderate |
| Heat Wave | Very Low |
| Winter Weather | Relatively Low |
| Lightning | Very Low |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Low |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
1 earthquake (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.5.
| Sep 2, 1999 | 8 km W of Amboy, Illinois | M3.5 | 138 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
662 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 13 fatalities, 435 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 15, 1968 | EF5 | 98 km | 13.1 mi | 5 |
| Mar 13, 1990 | EF4 | 36 km | 19.0 mi | 0 |
| Aug 12, 1974 | EF4 | 47 km | 5.0 mi | 0 |
| Aug 26, 1965 | EF4 | 100 km | 4.7 mi | 1 |
| Apr 11, 1965 | EF4 | 29 km | 91.5 mi | 1 |
| Apr 30, 1954 | EF4 | 61 km | 80.4 mi | 0 |
| May 25, 2008 | EF3 | 99 km | 32.0 mi | 0 |
| Jun 1, 2007 | EF3 | 94 km | 15.8 mi | 0 |
| May 21, 2004 | EF3 | 67 km | 3.0 mi | 0 |
| Jul 27, 1995 | EF3 | 77 km | 20.0 mi | 0 |
| May 9, 1995 | EF3 | 60 km | 10.0 mi | 0 |
| Jun 19, 1993 | EF3 | 34 km | 14.0 mi | 0 |
| Jun 19, 1993 | EF3 | 55 km | 9.0 mi | 0 |
| Jul 13, 1992 | EF3 | 13 km | 5.0 mi | 0 |
| Mar 13, 1990 | EF3 | 83 km | 15.5 mi | 0 |
| May 8, 1988 | EF3 | 44 km | 32.0 mi | 0 |
| May 8, 1988 | EF3 | 83 km | 16.0 mi | 0 |
| May 30, 1985 | EF3 | 93 km | 34.0 mi | 2 |
| Aug 15, 1978 | EF3 | 95 km | 6.4 mi | 0 |
| Jun 20, 1974 | EF3 | 63 km | 10.6 mi | 1 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
1 wildfire (100+ acres) recorded within 100 km. Largest: ACE AUTO (676 acres, 2011).
| Year | Name | Acres Burned | Distance |
| 2011 | ACE AUTO | 676 | 95 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 19°F (-7°C) | 1.1 in | Coldest, Driest |
| February | 24°F (-5°C) | 1.1 in | |
| March | 36°F (2°C) | 2.3 in | |
| April | 49°F (9°C) | 3.3 in | |
| May | 61°F (16°C) | 3.9 in | |
| June | 70°F (21°C) | 4.5 in | Wettest |
| July | 73°F (23°C) | 3.9 in | Warmest |
| August | 71°F (22°C) | 4.3 in | |
| September | 63°F (17°C) | 4.1 in | |
| October | 51°F (11°C) | 2.5 in | |
| November | 36°F (2°C) | 2.3 in | |
| December | 23°F (-5°C) | 1.7 in |
Onslow has a seasonal temperature swing of 53°F / from 19°F in January to 73°F in July. Total annual precipitation is 35.2 inches, with June being the wettest month (4.5") and January the driest (1.1").