Weather & Climate in Westmont, IL
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Westmont experiences four distinct seasons with an average annual temperature of 49°F (10°C). Winters average 23°F in January while summers reach 73°F in July. Annual precipitation totals 39.7 inches. The area receives 42.3 inches of snow annually, making winter weather a significant factor for residents. Air quality is rated Moderate with a median AQI of 54. 36% of days have good air quality. The city sits at an elevation of 758 feet.
Temperature
23°F Jan (-5°C)
73°F Jul (23°C)
| Annual Average | 49.2°F |
| 9% below US avg | |
| January Average | 23°F (-5°C) |
| July Average | 73°F (23°C) |
Geography
| Elevation | 758 ft (231 m) |
| Area | 5.1 sq mi (13.2 km²) |
| Population Density | 4,811/sq mi |
| Coordinates | 41.7944°N, 87.9729°W |
| Timezone | America/Chicago |
| County | Cook County County |
| Nearest Airport | Chicago Midway International (MDW) 11 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 54.0 |
| Rating | Moderate |
| Good Days % | 35.8% |
| Unhealthy Days | 11 |
Natural Hazard Risk
| Overall Risk | Very High |
| Risk Score | 100.0 / 100 |
| Social Vulnerability | 61.7 / 100 |
| Community Resilience | 73.3 / 100 |
Hazard Breakdown
| Tornado | Very High |
| Hurricane | Very Low |
| Earthquake | Relatively High |
| Wildfire | Very Low |
| Flood | Very High |
| Hail | Relatively High |
| Strong Wind | Very High |
| Heat Wave | Very High |
| Winter Weather | Very High |
| Lightning | Very High |
| Ice Storm | Very High |
| Drought | Very Low |
| Cold Wave | Very High |
| Landslide | Very Low |
| Coastal Flood | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
8 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M4.2.
| Jun 28, 2004 | 12 km NW of Dayton, Illinois | M4.2 | 86 km | 10 km |
| Feb 10, 2010 | 2 km NW of Lily Lake, Illinois | M3.8 | 48 km | 10 km |
| Sep 2, 1999 | 8 km W of Amboy, Illinois | M3.5 | 121 km | 5 km |
| Nov 4, 2013 | 1 km SSW of Lyons, Illinois | M3.2 | 12 km | 1 km |
| Jul 15, 2024 | 2 km WNW of Somonauk, Illinois | M3.1 | 64 km | 10 km |
| Mar 25, 2015 | 3 km WNW of Lake in the Hills, Illinois | M2.9 | 55 km | 6 km |
| Jun 10, 2013 | 4 km NNE of Virgil, Illinois | M2.6 | 49 km | 5 km |
| Mar 15, 2025 | 6 km W of Dwight, Illinois | M2.6 | 90 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990-2025). Sorted by magnitude.
Tornado History
572 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 111 fatalities, 2,173 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Aug 28, 1990 | EF5 | 34 km | 16.4 mi | 29 |
| Jun 29, 1979 | EF4 | 37 km | 5.4 mi | 0 |
| Jun 13, 1976 | EF4 | 14 km | 3.3 mi | 2 |
| Sep 28, 1972 | EF4 | 55 km | 5.2 mi | 0 |
| Apr 21, 1967 | EF4 | 18 km | 15.0 mi | 33 |
| Apr 21, 1967 | EF4 | 47 km | 8.8 mi | 1 |
| Apr 21, 1967 | EF4 | 92 km | 25.5 mi | 24 |
| Apr 11, 1965 | EF4 | 58 km | 9.1 mi | 6 |
| Apr 17, 1963 | EF4 | 69 km | 57.3 mi | 1 |
| Jun 20, 2021 | EF3 | 19 km | 17.6 mi | 0 |
| Feb 28, 2017 | EF3 | 97 km | 11.5 mi | 2 |
| Jun 22, 2015 | EF3 | 64 km | 16.3 mi | 0 |
| Jun 5, 2010 | EF3 | 100 km | 8.6 mi | 0 |
| Jun 5, 2010 | EF3 | 83 km | 7.8 mi | 0 |
| Jan 7, 2008 | EF3 | 97 km | 13.2 mi | 0 |
| Jan 7, 2008 | EF3 | 89 km | 10.8 mi | 0 |
| Mar 27, 1991 | EF3 | 26 km | 15.0 mi | 0 |
| Apr 27, 1984 | EF3 | 40 km | 9.0 mi | 1 |
| Apr 2, 1982 | EF3 | 83 km | 12.0 mi | 0 |
| Jun 30, 1977 | EF3 | 89 km | 6.1 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950-2024, US only).
Tsunami History
1 tsunami recorded within 500 km. Highest wave on record: 3.0 m (10 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1954 | MICHIGAN CITY, IN (LAKE MICHIGAN) | Avalanche | 3.0 m | 7 | 91 km |
Source: NOAA/NCEI Historical Tsunami Database.
Wildfire History
13 wildfires (100+ acres) recorded within 100 km. Largest: UNNAMED (1,741 acres, 2019).
| Year | Name | Acres Burned | Distance |
| 2019 | UNNAMED | 1,741 | 49 km |
| 2019 | UNNAMED | 1,664 | 49 km |
| 2000 | UNNAMED | 1,602 | 96 km |
| 2021 | NORTHEAST PRAIRIE UNIT 3 | 978 | 48 km |
| 2024 | NORTHEAST PRAIRIE 3 RX | 938 | 46 km |
| 1986 | OGDEN DUNS | 863 | 66 km |
| 2021 | UNNAMED | 738 | 46 km |
| 2021 | MIDDLE GRANT CREEK | 700 | 50 km |
| 2019 | UNNAMED | 698 | 46 km |
| 2024 | IBSP SOUTH F1 RX | 690 | 69 km |
| 2021 | 21-INDU TOLLESTON DUNES EAST | 594 | 67 km |
| 2017 | UNNAMED | 549 | 50 km |
| 2017 | 17 INDU COWLES DUNES | 522 | 74 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 23°F (-5°C) | 2.2 in | Coldest, Driest |
| February | 26°F (-3°C) | 2.3 in | |
| March | 37°F (3°C) | 2.5 in | |
| April | 48°F (9°C) | 3.8 in | |
| May | 59°F (15°C) | 4.2 in | |
| June | 69°F (21°C) | 4.1 in | |
| July | 73°F (23°C) | 4.0 in | Warmest |
| August | 71°F (22°C) | 4.6 in | Wettest |
| September | 64°F (18°C) | 3.5 in | |
| October | 52°F (11°C) | 3.4 in | |
| November | 39°F (4°C) | 2.8 in | |
| December | 29°F (-2°C) | 2.4 in |
Westmont has a seasonal temperature swing of 50°F / from 23°F in January to 73°F in July. Total annual precipitation is 39.7 inches, with August being the wettest month (4.6") and January the driest (2.2").