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Weather & Climate in Harper, IA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Harper experiences four distinct seasons with an average annual temperature of 49°F (9°C). Winters average 21°F in January while summers reach 74°F in July. The area gets 275 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 37.4 inches. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 810 feet.
Temperature
21°F Jan (-6°C)
74°F Jul (23°C)
| Annual Average | 48.9°F |
| 9% below US avg | |
| January Average | 21°F (-6°C) |
| July Average | 74°F (23°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 810 ft (247 m) |
| Area | 0.1 sq mi (0.2 km²) |
| Population Density | 1,444/sq mi |
| Coordinates | 41.3637°N, 92.0509°W |
| Timezone | America/Chicago |
| County | Keokuk County County |
| Nearest Airport | Ottumwa Regional (OTM) 27 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 21.9 / 100 |
| Social Vulnerability | 21.6 / 100 |
| Community Resilience | 81.3 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Relatively Low |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Relatively Low |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Low |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Tornado History
558 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 10 fatalities, 267 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Mar 31, 2023 | EF4 | 6 km | 19.9 mi | 0 |
| Aug 12, 1974 | EF4 | 44 km | 2.0 mi | 0 |
| Apr 30, 1954 | EF4 | 86 km | 80.4 mi | 0 |
| Mar 31, 2023 | EF3 | 41 km | 26.1 mi | 0 |
| May 27, 2019 | EF3 | 78 km | 7.3 mi | 0 |
| Jul 19, 2018 | EF3 | 75 km | 9.2 mi | 0 |
| Jun 22, 2015 | EF3 | 92 km | 11.1 mi | 0 |
| Jun 1, 2007 | EF3 | 73 km | 15.8 mi | 0 |
| May 21, 2004 | EF3 | 79 km | 3.0 mi | 0 |
| Apr 8, 1999 | EF3 | 75 km | 16.0 mi | 0 |
| May 15, 1998 | EF3 | 28 km | 47.0 mi | 0 |
| May 4, 1977 | EF3 | 97 km | 17.8 mi | 0 |
| Nov 9, 1975 | EF3 | 99 km | 39.4 mi | 0 |
| May 31, 1971 | EF3 | 84 km | 9.4 mi | 0 |
| May 18, 1971 | EF3 | 60 km | 4.3 mi | 0 |
| May 18, 1971 | EF3 | 72 km | 4.3 mi | 0 |
| Apr 21, 1967 | EF3 | 42 km | 0.1 mi | 0 |
| Apr 16, 1967 | EF3 | 74 km | 19.4 mi | 2 |
| Jan 24, 1967 | EF3 | 55 km | 25.0 mi | 0 |
| Jan 24, 1967 | EF3 | 99 km | 4.3 mi | 1 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
9 wildfires (100+ acres) recorded within 100 km. Largest: UNIT 3 (1,206 acres, 1999).
| Year | Name | Acres Burned | Distance |
| 1999 | UNIT 3 | 1,206 | 85 km |
| 2002 | HSB 03 2 | 1,130 | 84 km |
| 2009 | UNNAMED | 939 | 59 km |
| 2010 | FOLEY | 786 | 56 km |
| 2000 | DESTRUST A | 756 | 84 km |
| 2011 | ACE AUTO | 676 | 52 km |
| 2006 | HSB 003 | 674 | 85 km |
| 2004 | HSB 009 | 608 | 84 km |
| 2011 | IRCP WUI ROFAE #2 FY11 | 510 | 63 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 21°F (-6°C) | 1.0 in | Coldest |
| February | 26°F (-3°C) | 0.9 in | Driest |
| March | 38°F (3°C) | 2.2 in | |
| April | 50°F (10°C) | 3.6 in | |
| May | 62°F (17°C) | 4.1 in | |
| June | 71°F (22°C) | 4.2 in | |
| July | 74°F (23°C) | 4.5 in | Warmest, Wettest |
| August | 73°F (23°C) | 4.2 in | |
| September | 65°F (18°C) | 4.1 in | |
| October | 53°F (12°C) | 2.8 in | |
| November | 38°F (4°C) | 2.4 in | |
| December | 26°F (-4°C) | 1.5 in |
Harper has a seasonal temperature swing of 53°F / from 21°F in January to 74°F in July. Total annual precipitation is 35.4 inches, with July being the wettest month (4.5") and February the driest (0.9").