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Weather & Climate in Potomac, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Potomac experiences four distinct seasons with an average annual temperature of 52°F (11°C). Winters average 26°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. The area receives 20.3 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 682 feet.
Temperature
26°F Jan (-3°C)
75°F Jul (24°C)
| Annual Average | 52.3°F |
| 3% below US avg | |
| January Average | 26°F (-3°C) |
| July Average | 75°F (24°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 682 ft (208 m) |
| Area | 0.5 sq mi (1.3 km²) |
| Population Density | 1,249/sq mi |
| Coordinates | 40.3067°N, 87.7976°W |
| Timezone | America/Chicago |
| County | Vermilion County County |
| Nearest Airport | Vermilion Regional (DNV) 13 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 78.8 / 100 |
| Social Vulnerability | 70.2 / 100 |
| Community Resilience | 87.0 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Hurricane | Very Low |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively Moderate |
| Strong Wind | Relatively High |
| Heat Wave | Relatively Moderate |
| Winter Weather | Relatively High |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively Moderate |
| Drought | Relatively Moderate |
| Cold Wave | Relatively High |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
7 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.8.
| Jun 17, 2021 | Illinois-Indiana border region | M3.8 | 69 km | 6 km |
| Dec 20, 1990 | 5 km S of Stilesville, Indiana | M3.7 | 128 km | 5 km |
| Apr 14, 2000 | 4 km NW of Heritage Lake, Indiana | M3.6 | 108 km | 5 km |
| May 13, 2025 | 7 km SSW of Lerna, Illinois | M3.3 | 115 km | 10 km |
| Dec 17, 1990 | Illinois-Indiana border region | M3.2 | 69 km | 10 km |
| Dec 16, 1996 | 3 km NNE of Terre Haute, Indiana | M3.1 | 96 km | 5 km |
| Mar 15, 2025 | 6 km W of Dwight, Illinois | M2.6 | 105 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
645 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 61 fatalities, 836 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Apr 26, 1994 | EF4 | 74 km | 14.0 mi | 3 |
| Mar 20, 1976 | EF4 | 70 km | 16.7 mi | 0 |
| Apr 3, 1974 | EF4 | 61 km | 108.7 mi | 18 |
| Apr 11, 1965 | EF4 | 82 km | 21.8 mi | 0 |
| Apr 11, 1965 | EF4 | 85 km | 45.7 mi | 28 |
| Nov 17, 2013 | EF3 | 69 km | 18.7 mi | 0 |
| Nov 17, 2013 | EF3 | 32 km | 29.8 mi | 0 |
| Nov 17, 2013 | EF3 | 82 km | 37.9 mi | 0 |
| Jun 5, 2010 | EF3 | 84 km | 7.8 mi | 0 |
| Apr 19, 1996 | EF3 | 25 km | 2.0 mi | 1 |
| Apr 19, 1996 | EF3 | 47 km | 4.0 mi | 0 |
| Apr 2, 1982 | EF3 | 84 km | 12.0 mi | 0 |
| Jun 2, 1980 | EF3 | 67 km | 18.1 mi | 1 |
| Jun 25, 1978 | EF3 | 71 km | 27.4 mi | 0 |
| Mar 12, 1976 | EF3 | 78 km | 38.5 mi | 1 |
| Aug 10, 1974 | EF3 | 90 km | 0.1 mi | 0 |
| Apr 3, 1974 | EF3 | 52 km | 5.9 mi | 1 |
| Apr 3, 1974 | EF3 | 74 km | 7.4 mi | 0 |
| Apr 3, 1974 | EF3 | 27 km | 25.9 mi | 0 |
| Apr 3, 1974 | EF3 | 46 km | 14.9 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
1 wildfire (100+ acres) recorded within 100 km. Largest: UNNAMED (1,602 acres, 2000).
| Year | Name | Acres Burned | Distance |
| 2000 | UNNAMED | 1,602 | 78 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 26°F (-3°C) | 1.8 in | Coldest, Driest |
| February | 28°F (-2°C) | 1.8 in | |
| March | 40°F (4°C) | 3.1 in | |
| April | 51°F (10°C) | 3.9 in | |
| May | 62°F (17°C) | 4.3 in | Wettest |
| June | 71°F (22°C) | 4.2 in | |
| July | 75°F (24°C) | 4.3 in | Warmest |
| August | 72°F (22°C) | 3.9 in | |
| September | 66°F (19°C) | 3.1 in | |
| October | 54°F (12°C) | 3.0 in | |
| November | 42°F (5°C) | 3.2 in | |
| December | 30°F (-1°C) | 2.7 in |
Potomac has a seasonal temperature swing of 49°F / from 26°F in January to 75°F in July. Total annual precipitation is 39.3 inches, with May being the wettest month (4.3") and January the driest (1.8").