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Weather & Climate in Hennepin, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Hennepin experiences four distinct seasons with an average annual temperature of 51°F (11°C). Winters average 25°F in January while summers reach 75°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 38.6 inches. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 535 feet.
Temperature
25°F Jan (-4°C)
75°F Jul (24°C)
| Annual Average | 51.4°F |
| 5% below US avg | |
| January Average | 25°F (-4°C) |
| July Average | 75°F (24°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 535 ft (163 m) |
| Area | 5.3 sq mi (13.8 km²) |
| Population Density | 149/sq mi |
| Coordinates | 41.2505°N, 89.3141°W |
| Timezone | America/Chicago |
| County | Putnam County County |
| Nearest Airport | Illinois Valley Regional-Walter A Duncan Field (VYS) 11 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 9.2 / 100 |
| Social Vulnerability | 34.8 / 100 |
| Community Resilience | 79.9 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Very Low |
| Strong Wind | Relatively Low |
| Heat Wave | Very Low |
| Winter Weather | Very Low |
| Lightning | Very Low |
| Ice Storm | Very Low |
| Drought | Relatively Low |
| Cold Wave | Relatively Low |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
8 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M4.2.
| Jun 28, 2004 | 12 km NW of Dayton, Illinois | M4.2 | 42 km | 10 km |
| Feb 10, 2010 | 2 km NW of Lily Lake, Illinois | M3.8 | 105 km | 10 km |
| Sep 2, 1999 | 8 km W of Amboy, Illinois | M3.5 | 53 km | 5 km |
| Nov 4, 2013 | 1 km SSW of Lyons, Illinois | M3.2 | 138 km | 1 km |
| Jul 15, 2024 | 2 km WNW of Somonauk, Illinois | M3.1 | 67 km | 10 km |
| Mar 25, 2015 | 3 km WNW of Lake in the Hills, Illinois | M2.9 | 131 km | 6 km |
| Jun 10, 2013 | 4 km NNE of Virgil, Illinois | M2.6 | 106 km | 5 km |
| Mar 15, 2025 | 6 km W of Dwight, Illinois | M2.6 | 71 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
663 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 53 fatalities, 894 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Aug 28, 1990 | EF5 | 94 km | 16.4 mi | 29 |
| Apr 9, 2015 | EF4 | 67 km | 30.1 mi | 2 |
| Nov 17, 2013 | EF4 | 73 km | 46.4 mi | 3 |
| Jul 13, 2004 | EF4 | 50 km | 9.6 mi | 0 |
| Mar 29, 1981 | EF4 | 71 km | 5.1 mi | 0 |
| Jun 29, 1979 | EF4 | 95 km | 5.4 mi | 0 |
| Jun 29, 1976 | EF4 | 62 km | 4.9 mi | 0 |
| Feb 28, 2017 | EF3 | 38 km | 17.8 mi | 0 |
| Feb 28, 2017 | EF3 | 32 km | 11.5 mi | 2 |
| Jun 22, 2015 | EF3 | 78 km | 16.3 mi | 0 |
| Jun 5, 2010 | EF3 | 52 km | 8.6 mi | 0 |
| Apr 20, 2004 | EF3 | 3 km | 15.8 mi | 8 |
| May 10, 2003 | EF3 | 92 km | 17.5 mi | 0 |
| May 9, 1995 | EF3 | 41 km | 22.0 mi | 0 |
| Mar 13, 1990 | EF3 | 89 km | 15.5 mi | 0 |
| Apr 27, 1984 | EF3 | 89 km | 9.0 mi | 1 |
| Aug 5, 1979 | EF3 | 88 km | 5.7 mi | 0 |
| Jun 30, 1977 | EF3 | 45 km | 6.1 mi | 0 |
| Mar 12, 1976 | EF3 | 91 km | 22.6 mi | 0 |
| Mar 4, 1976 | EF3 | 22 km | 0.8 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
3 wildfires (100+ acres) recorded within 100 km. Largest: UNNAMED (1,741 acres, 2019).
| Year | Name | Acres Burned | Distance |
| 2019 | UNNAMED | 1,741 | 97 km |
| 2021 | MIDDLE GRANT CREEK | 700 | 98 km |
| 2017 | UNNAMED | 549 | 98 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 25°F (-4°C) | 1.4 in | Coldest |
| February | 26°F (-3°C) | 1.3 in | Driest |
| March | 38°F (3°C) | 2.6 in | |
| April | 50°F (10°C) | 3.6 in | |
| May | 61°F (16°C) | 3.7 in | |
| June | 70°F (21°C) | 4.0 in | Wettest |
| July | 75°F (24°C) | 3.9 in | Warmest |
| August | 72°F (22°C) | 3.8 in | |
| September | 65°F (18°C) | 3.9 in | |
| October | 53°F (12°C) | 2.6 in | |
| November | 40°F (4°C) | 2.6 in | |
| December | 27°F (-3°C) | 2.1 in |
Hennepin has a seasonal temperature swing of 50°F / from 25°F in January to 75°F in July. Total annual precipitation is 35.5 inches, with June being the wettest month (4.0") and February the driest (1.3").