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Weather & Climate in Plymouth, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Plymouth experiences four distinct seasons with an average annual temperature of 52°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 40.9 inches. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 644 feet.
Temperature
25°F Jan (-4°C)
75°F Jul (24°C)
| Annual Average | 51.7°F |
| 4% below US avg | |
| January Average | 25°F (-4°C) |
| July Average | 75°F (24°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 644 ft (196 m) |
| Area | 0.2 sq mi (0.6 km²) |
| Population Density | 898/sq mi |
| Coordinates | 40.2921°N, 90.9163°W |
| Timezone | America/Chicago |
| County | McDonough County County |
| Nearest Airport | Quincy Regional-Baldwin Field (UIN) 28 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 37.5 / 100 |
| Social Vulnerability | 61.9 / 100 |
| Community Resilience | 74.3 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Relatively Moderate |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Moderate |
| Winter Weather | Relatively Low |
| Lightning | Relatively Low |
| Ice Storm | Relatively Moderate |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Moderate |
| 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: M2.9.
| Feb 8, 2004 | 6 km SSW of Stoutsville, Missouri | M2.9 | 121 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
475 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 10 fatalities, 379 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 13, 1995 | EF4 | 53 km | 7.0 mi | 0 |
| May 13, 1995 | EF4 | 46 km | 50.0 mi | 0 |
| Apr 4, 2023 | EF3 | 51 km | 19.9 mi | 0 |
| Dec 31, 2010 | EF3 | 96 km | 3.6 mi | 0 |
| May 10, 2003 | EF3 | 98 km | 12.0 mi | 0 |
| Apr 8, 1999 | EF3 | 46 km | 7.5 mi | 0 |
| May 13, 1995 | EF3 | 85 km | 25.0 mi | 0 |
| Jun 21, 1981 | EF3 | 25 km | 8.8 mi | 1 |
| Jul 23, 1975 | EF3 | 57 km | 11.1 mi | 0 |
| Jul 23, 1975 | EF3 | 70 km | 14.0 mi | 2 |
| Jun 13, 1975 | EF3 | 71 km | 6.6 mi | 0 |
| Apr 13, 1974 | EF3 | 48 km | 11.0 mi | 0 |
| Sep 30, 1973 | EF3 | 7 km | 0.1 mi | 0 |
| May 1, 1973 | EF3 | 70 km | 3.6 mi | 2 |
| Apr 20, 1973 | EF3 | 97 km | 9.5 mi | 0 |
| May 15, 1968 | EF3 | 92 km | 12.6 mi | 0 |
| Jan 24, 1967 | EF3 | 62 km | 5.1 mi | 1 |
| Jan 24, 1967 | EF3 | 54 km | 4.3 mi | 1 |
| Aug 25, 1965 | EF3 | 72 km | 3.0 mi | 0 |
| Apr 21, 1964 | EF3 | 21 km | 14.1 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 | 92 km |
| 2002 | HSB 03 2 | 1,130 | 93 km |
| 2000 | DESTRUST A | 756 | 94 km |
| 2006 | HSB 003 | 674 | 92 km |
| 2004 | HSB 009 | 608 | 93 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 25°F (-4°C) | 1.4 in | Coldest, Driest |
| February | 29°F (-2°C) | 1.5 in | |
| March | 41°F (5°C) | 2.9 in | |
| April | 52°F (11°C) | 3.8 in | |
| May | 63°F (17°C) | 4.4 in | Wettest |
| June | 72°F (22°C) | 3.9 in | |
| July | 75°F (24°C) | 4.3 in | Warmest |
| August | 74°F (23°C) | 3.5 in | |
| September | 66°F (19°C) | 4.1 in | |
| October | 55°F (13°C) | 3.0 in | |
| November | 41°F (5°C) | 2.8 in | |
| December | 29°F (-2°C) | 2.2 in |
Plymouth has a seasonal temperature swing of 50°F / from 25°F in January to 75°F in July. Total annual precipitation is 37.8 inches, with May being the wettest month (4.4") and January the driest (1.4").