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Weather & Climate in Janesville, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Janesville experiences four distinct seasons with an average annual temperature of 53°F (12°C). Winters average 28°F in January while summers reach 76°F in July. The area gets 302 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 36.0 inches. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 690 feet.
Temperature
28°F Jan (-2°C)
76°F Jul (24°C)
| Annual Average | 53.4°F |
| 1% below US avg | |
| January Average | 28°F (-2°C) |
| July Average | 76°F (24°C) |
| Sunny Days | 302 days/yr |
Geography
| Elevation | 690 ft (210 m) |
| Area | 0.1 sq mi (0.2 km²) |
| Population Density | 233/sq mi |
| Coordinates | 39.3752°N, 88.2450°W |
| Timezone | America/Chicago |
| County | Cumberland County County |
| Nearest Airport | Terre Haute Regional (HUF) 50 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 25.9 / 100 |
| Social Vulnerability | 63.2 / 100 |
| Community Resilience | 88.1 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Relatively Low |
| Strong Wind | Relatively Low |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Very Low |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Low |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
46 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M5.2.
| Apr 18, 2008 | 7 km NNE of Bellmont, Illinois | M5.2 | 107 km | 14 km |
| Apr 18, 2008 | 9 km NNE of Bellmont, Illinois | M4.7 | 107 km | 15 km |
| Apr 21, 2008 | 7 km NNE of Bellmont, Illinois | M4.0 | 108 km | 18 km |
| Jun 17, 2021 | Illinois-Indiana border region | M3.8 | 97 km | 6 km |
| Sep 19, 2017 | 4 km N of Bellmont, Illinois | M3.8 | 110 km | 12 km |
| Nov 11, 1991 | 3 km W of Flat Rock, Illinois | M3.8 | 70 km | 0 km |
| Dec 20, 1990 | 5 km S of Stilesville, Indiana | M3.7 | 141 km | 5 km |
| Apr 25, 2008 | 8 km NNE of Bellmont, Illinois | M3.7 | 108 km | 13 km |
| Nov 20, 2012 | 7 km N of Bellmont, Illinois | M3.6 | 107 km | 19 km |
| Apr 14, 2000 | 4 km NW of Heritage Lake, Indiana | M3.6 | 135 km | 5 km |
| Mar 2, 1990 | 9 km NW of Vernon, Illinois | M3.4 | 99 km | 0 km |
| Jun 5, 2008 | 8 km WNW of Mount Carmel, Illinois | M3.4 | 108 km | 16 km |
| May 30, 2015 | 4 km ENE of Geff, Illinois | M3.4 | 102 km | 26 km |
| May 1, 2008 | 8 km NNE of Bellmont, Illinois | M3.3 | 108 km | 14 km |
| May 13, 2025 | 7 km SSW of Lerna, Illinois | M3.3 | 7 km | 10 km |
| Dec 17, 1990 | Illinois-Indiana border region | M3.2 | 128 km | 10 km |
| Oct 24, 1990 | 5 km ENE of Woodlawn, Illinois | M3.2 | 131 km | 1 km |
| Jan 29, 1993 | 7 km WNW of Brownstown, Illinois | M3.2 | 78 km | 5 km |
| Jul 1, 2017 | 9 km SSE of Mulberry Grove, Illinois | M3.1 | 103 km | 17 km |
| May 10, 2012 | 0 km NW of Emison, Indiana | M3.1 | 93 km | 11 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
546 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 21 fatalities, 421 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jun 2, 1990 | EF4 | 47 km | 12.5 mi | 0 |
| Jun 2, 1990 | EF4 | 92 km | 23.0 mi | 0 |
| Mar 20, 1976 | EF4 | 67 km | 63.7 mi | 0 |
| Mar 31, 2023 | EF3 | 55 km | 40.9 mi | 6 |
| Dec 1, 2018 | EF3 | 99 km | 12.5 mi | 0 |
| Nov 17, 2013 | EF3 | 96 km | 29.8 mi | 0 |
| Nov 17, 2013 | EF3 | 52 km | 18.7 mi | 0 |
| Apr 19, 1996 | EF3 | 87 km | 2.0 mi | 1 |
| Apr 19, 1996 | EF3 | 77 km | 4.0 mi | 0 |
| Apr 19, 1996 | EF3 | 94 km | 14.5 mi | 0 |
| Aug 21, 1977 | EF3 | 35 km | 26.9 mi | 6 |
| Aug 10, 1974 | EF3 | 20 km | 0.1 mi | 0 |
| Aug 10, 1974 | EF3 | 32 km | 0.1 mi | 0 |
| Apr 3, 1974 | EF3 | 66 km | 14.9 mi | 0 |
| Apr 3, 1974 | EF3 | 85 km | 20.9 mi | 1 |
| Apr 3, 1974 | EF3 | 67 km | 5.9 mi | 1 |
| Apr 1, 1974 | EF3 | 85 km | 3.3 mi | 0 |
| Apr 29, 1963 | EF3 | 77 km | 23.9 mi | 0 |
| Apr 29, 1963 | EF3 | 88 km | 5.6 mi | 0 |
| Apr 22, 1963 | EF3 | 47 km | 38.6 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 28°F (-2°C) | 2.1 in | Coldest, Driest |
| February | 31°F (-1°C) | 2.2 in | |
| March | 42°F (5°C) | 3.4 in | |
| April | 53°F (11°C) | 4.0 in | |
| May | 63°F (17°C) | 4.1 in | |
| June | 72°F (22°C) | 4.0 in | |
| July | 76°F (24°C) | 4.4 in | Warmest, Wettest |
| August | 74°F (23°C) | 3.5 in | |
| September | 67°F (20°C) | 3.2 in | |
| October | 56°F (13°C) | 3.1 in | |
| November | 43°F (6°C) | 3.7 in | |
| December | 32°F (-0°C) | 3.2 in |
Janesville has a seasonal temperature swing of 48°F / from 28°F in January to 76°F in July. Total annual precipitation is 41.0 inches, with July being the wettest month (4.4") and January the driest (2.1").