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Weather & Climate in Flat Rock, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Flat Rock enjoys a temperate climate with an average annual temperature of 56°F (13°C). Winters average 31°F in January while summers reach 77°F in July. The area gets 293 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 41.7 inches. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 500 feet.
Temperature
31°F Jan (-0°C)
77°F Jul (25°C)
| Annual Average | 55.7°F |
| 3% above US avg | |
| January Average | 31°F (-0°C) |
| July Average | 77°F (25°C) |
| Sunny Days | 293 days/yr |
Geography
| Elevation | 500 ft (152 m) |
| Area | 0.9 sq mi (2.2 km²) |
| Population Density | 421/sq mi |
| Coordinates | 38.9037°N, 87.6734°W |
| Timezone | America/Chicago |
| County | Lawrence County County |
| Nearest Airport | Lawrenceville-Vincennes International (LWV) 10 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 49.2 / 100 |
| Social Vulnerability | 57.4 / 100 |
| Community Resilience | 47.3 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Very Low |
| Strong Wind | Relatively Low |
| 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)
Earthquake History
60 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 | 54 km | 14 km |
| Apr 18, 2008 | 9 km NNE of Bellmont, Illinois | M4.7 | 52 km | 15 km |
| Jun 18, 2002 | 6 km SW of Parkers Settlement, Indiana | M4.6 | 101 km | 16 km |
| Apr 21, 2008 | 7 km NNE of Bellmont, Illinois | M4.0 | 54 km | 18 km |
| Jan 24, 1990 | 6 km WNW of Alton, Indiana | M3.9 | 134 km | 10 km |
| Dec 7, 2000 | 7 km W of Evansville, Indiana | M3.9 | 104 km | 5 km |
| Jun 17, 2021 | Illinois-Indiana border region | M3.8 | 108 km | 6 km |
| Nov 11, 1991 | 3 km W of Flat Rock, Illinois | M3.8 | 3 km | 0 km |
| Jan 27, 1990 | 6 km N of Alton, Indiana | M3.8 | 135 km | 5 km |
| Sep 19, 2017 | 4 km N of Bellmont, Illinois | M3.8 | 57 km | 12 km |
| Dec 20, 1990 | 5 km S of Stilesville, Indiana | M3.7 | 118 km | 5 km |
| Apr 25, 2008 | 8 km NNE of Bellmont, Illinois | M3.7 | 53 km | 13 km |
| Jan 2, 2006 | 3 km NNE of Eldorado, Illinois | M3.6 | 135 km | 7 km |
| Nov 20, 2012 | 7 km N of Bellmont, Illinois | M3.6 | 54 km | 19 km |
| Apr 14, 2000 | 4 km NW of Heritage Lake, Indiana | M3.6 | 124 km | 5 km |
| May 30, 2015 | 4 km ENE of Geff, Illinois | M3.4 | 77 km | 26 km |
| Jun 5, 2008 | 8 km WNW of Mount Carmel, Illinois | M3.4 | 52 km | 16 km |
| Mar 2, 1990 | 9 km NW of Vernon, Illinois | M3.4 | 130 km | 0 km |
| May 1, 2008 | 8 km NNE of Bellmont, Illinois | M3.3 | 53 km | 14 km |
| May 13, 2025 | 7 km SSW of Lerna, Illinois | M3.3 | 76 km | 10 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
474 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 21 fatalities, 521 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jun 2, 1990 | EF4 | 52 km | 12.5 mi | 0 |
| Jun 2, 1990 | EF4 | 100 km | 11.0 mi | 1 |
| Jun 2, 1990 | EF4 | 51 km | 13.0 mi | 6 |
| Jun 2, 1990 | EF4 | 78 km | 23.0 mi | 0 |
| Jan 7, 1989 | EF4 | 48 km | 19.0 mi | 0 |
| Mar 31, 2023 | EF3 | 34 km | 40.9 mi | 6 |
| Mar 31, 2023 | EF3 | 93 km | 5.9 mi | 2 |
| Feb 28, 2017 | EF3 | 94 km | 44.1 mi | 1 |
| Mar 8, 2009 | EF3 | 93 km | 1.1 mi | 0 |
| Nov 15, 2005 | EF3 | 53 km | 12.0 mi | 0 |
| Sep 20, 2002 | EF3 | 98 km | 112.0 mi | 0 |
| Nov 22, 1992 | EF3 | 96 km | 5.3 mi | 0 |
| Jun 2, 1990 | EF3 | 61 km | 7.0 mi | 0 |
| Apr 3, 1989 | EF3 | 73 km | 3.1 mi | 0 |
| Aug 10, 1974 | EF3 | 84 km | 0.1 mi | 0 |
| Aug 10, 1974 | EF3 | 61 km | 0.1 mi | 0 |
| Apr 1, 1974 | EF3 | 21 km | 3.3 mi | 0 |
| Oct 24, 1967 | EF3 | 89 km | 0.1 mi | 0 |
| Apr 29, 1963 | EF3 | 23 km | 23.9 mi | 0 |
| Apr 29, 1963 | EF3 | 87 km | 5.6 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 31°F (-0°C) | 2.4 in | Coldest, Driest |
| February | 33°F (0°C) | 2.5 in | |
| March | 44°F (6°C) | 3.9 in | |
| April | 54°F (12°C) | 4.1 in | |
| May | 64°F (18°C) | 4.6 in | Wettest |
| June | 73°F (23°C) | 4.0 in | |
| July | 77°F (25°C) | 4.3 in | Warmest |
| August | 75°F (24°C) | 3.7 in | |
| September | 68°F (20°C) | 3.3 in | |
| October | 56°F (13°C) | 3.0 in | |
| November | 45°F (7°C) | 3.9 in | |
| December | 34°F (1°C) | 3.3 in |
Flat Rock has a seasonal temperature swing of 46°F / from 31°F in January to 77°F in July. Total annual precipitation is 42.8 inches, with May being the wettest month (4.6") and January the driest (2.4").