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Weather & Climate in Grinnell, IA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Grinnell 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 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 38.2 inches. The area receives 31.0 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 1,003 feet.
Temperature
19°F Jan (-7°C)
73°F Jul (23°C)
| Annual Average | 47.5°F |
| 12% below US avg | |
| January Average | 19°F (-7°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 1,003 ft (306 m) |
| Area | 5.6 sq mi (14.4 km²) |
| Population Density | 1,674/sq mi |
| Coordinates | 41.7352°N, 92.7249°W |
| Timezone | America/Chicago |
| County | Poweshiek County County |
| Nearest Airport | Ottumwa Regional (OTM) 46 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 31.3 / 100 |
| Social Vulnerability | 21.4 / 100 |
| Community Resilience | 84.9 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Relatively Moderate |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Very Low |
| Ice Storm | Relatively Low |
| Drought | Relatively High |
| Cold Wave | Relatively Low |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Tornado History
671 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 27 fatalities, 544 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 25, 2008 | EF5 | 92 km | 41.0 mi | 9 |
| Jun 13, 1976 | EF5 | 97 km | 21.3 mi | 0 |
| Mar 31, 2023 | EF4 | 75 km | 19.9 mi | 0 |
| May 30, 1989 | EF4 | 71 km | 11.0 mi | 0 |
| Sep 28, 1986 | EF4 | 73 km | 20.0 mi | 0 |
| Aug 12, 1974 | EF4 | 45 km | 2.0 mi | 0 |
| Jun 18, 1974 | EF4 | 74 km | 15.3 mi | 2 |
| Aug 26, 1965 | EF4 | 76 km | 4.7 mi | 1 |
| Apr 30, 1954 | EF4 | 90 km | 80.4 mi | 0 |
| Mar 31, 2023 | EF3 | 82 km | 26.1 mi | 0 |
| Aug 20, 2019 | EF3 | 85 km | 5.4 mi | 0 |
| Jul 19, 2018 | EF3 | 46 km | 8.4 mi | 0 |
| Jul 19, 2018 | EF3 | 35 km | 9.2 mi | 0 |
| Jun 22, 2015 | EF3 | 71 km | 11.1 mi | 0 |
| May 21, 2004 | EF3 | 83 km | 3.0 mi | 0 |
| May 11, 2000 | EF3 | 90 km | 18.6 mi | 1 |
| Apr 8, 1999 | EF3 | 99 km | 39.0 mi | 0 |
| May 15, 1998 | EF3 | 97 km | 47.0 mi | 0 |
| Mar 22, 1991 | EF3 | 77 km | 43.0 mi | 0 |
| Mar 13, 1990 | EF3 | 63 km | 9.0 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
5 wildfires (100+ acres) recorded within 100 km. Largest: NEAL SMITH WUI 2016 1 (1,050 acres, 2016).
| Year | Name | Acres Burned | Distance |
| 2016 | NEAL SMITH WUI 2016 1 | 1,050 | 49 km |
| 2009 | UNNAMED | 939 | 41 km |
| 2010 | FOLEY | 786 | 44 km |
| 2011 | ACE AUTO | 676 | 52 km |
| 2011 | IRCP WUI ROFAE #2 FY11 | 510 | 37 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 (-4°C) | 1.1 in | |
| March | 36°F (2°C) | 2.3 in | |
| April | 49°F (9°C) | 3.4 in | |
| May | 61°F (16°C) | 4.1 in | |
| June | 70°F (21°C) | 4.7 in | Wettest |
| July | 73°F (23°C) | 4.1 in | Warmest |
| August | 71°F (22°C) | 4.3 in | |
| September | 63°F (17°C) | 4.0 in | |
| October | 52°F (11°C) | 2.7 in | |
| November | 37°F (3°C) | 2.1 in | |
| December | 24°F (-5°C) | 1.5 in |
Grinnell has a seasonal temperature swing of 53°F / from 19°F in January to 73°F in July. Total annual precipitation is 35.3 inches, with June being the wettest month (4.7") and January the driest (1.1").