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Weather & Climate in Monmouth, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Monmouth experiences four distinct seasons with an average annual temperature of 51°F (10°C). Winters average 23°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 39.4 inches. The area receives 25.6 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 759 feet.
Temperature
23°F Jan (-5°C)
74°F Jul (23°C)
| Annual Average | 50.6°F |
| 6% below US avg | |
| January Average | 23°F (-5°C) |
| July Average | 74°F (23°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 759 ft (231 m) |
| Area | 4.3 sq mi (11.0 km²) |
| Population Density | 2,074/sq mi |
| Coordinates | 40.9142°N, 90.6431°W |
| Timezone | America/Chicago |
| County | Warren County County |
| Nearest Airport | Southeast Iowa Regional (BRL) 27 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 15.5 / 100 |
| Social Vulnerability | 22.8 / 100 |
| Community Resilience | 90.6 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Relatively 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
1 earthquake (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.5.
| Sep 2, 1999 | 8 km W of Amboy, Illinois | M3.5 | 135 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
644 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 11 fatalities, 553 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Nov 17, 2013 | EF4 | 96 km | 46.4 mi | 3 |
| May 13, 1995 | EF4 | 67 km | 50.0 mi | 0 |
| May 13, 1995 | EF4 | 67 km | 7.0 mi | 0 |
| Jun 29, 1976 | EF4 | 76 km | 4.9 mi | 0 |
| Apr 4, 2023 | EF3 | 70 km | 19.9 mi | 0 |
| Jun 1, 2007 | EF3 | 61 km | 15.8 mi | 0 |
| May 10, 2003 | EF3 | 95 km | 17.5 mi | 0 |
| Apr 8, 1999 | EF3 | 93 km | 7.5 mi | 0 |
| May 15, 1998 | EF3 | 100 km | 47.0 mi | 0 |
| May 13, 1995 | EF3 | 82 km | 25.0 mi | 0 |
| May 9, 1995 | EF3 | 83 km | 22.0 mi | 0 |
| May 9, 1995 | EF3 | 76 km | 10.0 mi | 0 |
| Mar 13, 1990 | EF3 | 82 km | 15.5 mi | 0 |
| May 8, 1988 | EF3 | 94 km | 32.0 mi | 0 |
| Jun 21, 1981 | EF3 | 76 km | 8.8 mi | 1 |
| Aug 15, 1978 | EF3 | 41 km | 6.4 mi | 0 |
| Mar 4, 1976 | EF3 | 95 km | 0.8 mi | 0 |
| Jul 23, 1975 | EF3 | 55 km | 14.0 mi | 2 |
| Jul 23, 1975 | EF3 | 48 km | 11.1 mi | 0 |
| Jun 13, 1975 | EF3 | 42 km | 6.6 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
5 wildfires (100+ acres) recorded within 100 km. Largest: UNIT 3 (1,206 acres, 1999).
| Year | Name | Acres Burned | Distance |
| 1999 | UNIT 3 | 1,206 | 44 km |
| 2002 | HSB 03 2 | 1,130 | 45 km |
| 2000 | DESTRUST A | 756 | 45 km |
| 2006 | HSB 003 | 674 | 44 km |
| 2004 | HSB 009 | 608 | 44 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 23°F (-5°C) | 1.5 in | Coldest, Driest |
| February | 27°F (-3°C) | 1.5 in | |
| March | 39°F (4°C) | 2.8 in | |
| April | 51°F (11°C) | 3.8 in | |
| May | 62°F (17°C) | 4.1 in | |
| June | 71°F (22°C) | 4.2 in | |
| July | 74°F (23°C) | 4.4 in | Warmest, Wettest |
| August | 73°F (23°C) | 3.9 in | |
| September | 65°F (18°C) | 3.8 in | |
| October | 53°F (12°C) | 2.9 in | |
| November | 39°F (4°C) | 2.6 in | |
| December | 27°F (-3°C) | 2.2 in |
Monmouth has a seasonal temperature swing of 51°F / from 23°F in January to 74°F in July. Total annual precipitation is 37.6 inches, with July being the wettest month (4.4") and January the driest (1.5").