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Weather & Climate in Delavan, WI
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Delavan experiences four distinct seasons with an average annual temperature of 48°F (9°C). Winters average 21°F in January while summers reach 72°F in July. The area gets 260 sunny days per year, above the national average. Annual precipitation totals 36.7 inches. Air quality is rated Good with a median AQI of 38. The city sits at an elevation of 936 feet.
Temperature
21°F Jan (-6°C)
72°F Jul (22°C)
| Annual Average | 47.6°F |
| 12% below US avg | |
| January Average | 21°F (-6°C) |
| July Average | 72°F (22°C) |
| Sunny Days | 260 days/yr |
Geography
| Elevation | 936 ft (285 m) |
| Area | 7.2 sq mi (18.7 km²) |
| Population Density | 1,151/sq mi |
| Coordinates | 42.6305°N, 88.6298°W |
| Timezone | America/Chicago |
| County | Walworth County County |
| Nearest Airport | Southern Wisconsin Regional (JVL) 21 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 38.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 74.8 / 100 |
| Social Vulnerability | 20.8 / 100 |
| Community Resilience | 80.3 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively High |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively Low |
| Drought | Relatively Low |
| Cold Wave | Relatively Moderate |
| 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: M4.2.
| Jun 28, 2004 | 12 km NW of Dayton, Illinois | M4.2 | 132 km | 10 km |
| Feb 10, 2010 | 2 km NW of Lily Lake, Illinois | M3.8 | 74 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 | 114 km | 1 km |
| Jul 15, 2024 | 2 km WNW of Somonauk, Illinois | M3.1 | 110 km | 10 km |
| Mar 25, 2015 | 3 km WNW of Lake in the Hills, Illinois | M2.9 | 54 km | 6 km |
| Jun 10, 2013 | 4 km NNE of Virgil, Illinois | M2.6 | 72 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
559 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 49 fatalities, 1,326 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Apr 27, 1984 | EF4 | 44 km | 6.5 mi | 1 |
| Apr 4, 1981 | EF4 | 96 km | 1.8 mi | 3 |
| Sep 28, 1972 | EF4 | 74 km | 5.2 mi | 0 |
| Apr 21, 1967 | EF4 | 52 km | 25.5 mi | 24 |
| Apr 21, 1967 | EF4 | 61 km | 8.8 mi | 1 |
| Apr 11, 1965 | EF4 | 50 km | 9.1 mi | 6 |
| Jun 16, 2014 | EF3 | 86 km | 1.0 mi | 0 |
| Jan 7, 2008 | EF3 | 26 km | 10.8 mi | 0 |
| Jan 7, 2008 | EF3 | 31 km | 13.2 mi | 0 |
| Aug 18, 2005 | EF3 | 73 km | 18.6 mi | 1 |
| Jun 17, 1992 | EF3 | 79 km | 16.0 mi | 0 |
| Jun 5, 1980 | EF3 | 57 km | 10.7 mi | 0 |
| Apr 7, 1980 | EF3 | 98 km | 1.2 mi | 0 |
| Jun 4, 1975 | EF3 | 83 km | 2.3 mi | 0 |
| Apr 21, 1974 | EF3 | 97 km | 58.6 mi | 2 |
| Aug 2, 1967 | EF3 | 87 km | 0.1 mi | 2 |
| Jan 24, 1967 | EF3 | 61 km | 24.9 mi | 0 |
| Jul 19, 1963 | EF3 | 32 km | 10.6 mi | 0 |
| Jun 22, 2024 | EF2 | 39 km | 6.0 mi | 0 |
| Feb 8, 2024 | EF2 | 58 km | 25.9 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
5 wildfires (100+ acres) recorded within 100 km. Largest: UNNAMED (1,524 acres, 2006).
| Year | Name | Acres Burned | Distance |
| 2006 | UNNAMED | 1,524 | 99 km |
| 2010 | RX BURN | 1,236 | 99 km |
| 2024 | IBSP SOUTH F1 RX | 690 | 71 km |
| 2024 | RX-HWY Y - SOUTH | 553 | 39 km |
| 2009 | COLD SPRINGS | 552 | 82 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 21°F (-6°C) | 1.5 in | Coldest |
| February | 23°F (-5°C) | 1.2 in | Driest |
| March | 34°F (1°C) | 2.5 in | |
| April | 46°F (8°C) | 3.5 in | |
| May | 58°F (14°C) | 3.4 in | |
| June | 68°F (20°C) | 4.0 in | |
| July | 72°F (22°C) | 4.2 in | Warmest, Wettest |
| August | 70°F (21°C) | 4.1 in | |
| September | 62°F (17°C) | 3.9 in | |
| October | 50°F (10°C) | 2.6 in | |
| November | 37°F (3°C) | 2.6 in | |
| December | 24°F (-4°C) | 2.0 in |
Delavan has a seasonal temperature swing of 51°F / from 21°F in January to 72°F in July. Total annual precipitation is 35.5 inches, with July being the wettest month (4.2") and February the driest (1.2").