All Countries
Weather & Climate in Merton, WI
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Merton experiences four distinct seasons with an average annual temperature of 47°F (8°C). Winters average 19°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 36.8 inches. Air quality is rated Good with a median AQI of 38. The city sits at an elevation of 974 feet.
Temperature
19°F Jan (-7°C)
72°F Jul (22°C)
| Annual Average | 46.5°F |
| 14% below US avg | |
| January Average | 19°F (-7°C) |
| July Average | 72°F (22°C) |
| Sunny Days | 260 days/yr |
Geography
| Elevation | 974 ft (297 m) |
| Area | 1.2 sq mi (3.1 km²) |
| Population Density | 1,053/sq mi |
| Coordinates | 43.1437°N, 88.3123°W |
| Timezone | America/Chicago |
| County | Waukesha County County |
| Nearest Airport | General Mitchell International (MKE) 25 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 38.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 88.9 / 100 |
| Social Vulnerability | 10.6 / 100 |
| Community Resilience | 97.4 / 100 |
Hazard Breakdown
| Tornado | Relatively High |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively High |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Moderate |
| Winter Weather | Relatively High |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively Moderate |
| Drought | Relatively Low |
| Cold Wave | Relatively High |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
3 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.8.
| Feb 10, 2010 | 2 km NW of Lily Lake, Illinois | M3.8 | 132 km | 10 km |
| Mar 25, 2015 | 3 km WNW of Lake in the Hills, Illinois | M2.9 | 106 km | 6 km |
| Jun 10, 2013 | 4 km NNE of Virgil, Illinois | M2.6 | 129 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
459 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 16 fatalities, 529 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 18, 1996 | EF5 | 67 km | 13.3 mi | 0 |
| Apr 27, 1984 | EF4 | 19 km | 6.5 mi | 1 |
| Apr 4, 1981 | EF4 | 33 km | 1.8 mi | 3 |
| Apr 21, 1974 | EF4 | 79 km | 26.0 mi | 0 |
| Aug 22, 1964 | EF4 | 41 km | 2.2 mi | 0 |
| Sep 26, 1951 | EF4 | 84 km | 9.0 mi | 1 |
| Jan 7, 2008 | EF3 | 66 km | 10.8 mi | 0 |
| Jan 7, 2008 | EF3 | 94 km | 13.2 mi | 0 |
| Aug 18, 2005 | EF3 | 94 km | 18.6 mi | 1 |
| Jun 23, 2004 | EF3 | 86 km | 33.3 mi | 0 |
| Jun 23, 2004 | EF3 | 78 km | 7.6 mi | 1 |
| Jun 8, 1984 | EF3 | 82 km | 29.0 mi | 0 |
| Jun 5, 1980 | EF3 | 37 km | 10.7 mi | 0 |
| Apr 7, 1980 | EF3 | 65 km | 1.2 mi | 0 |
| Jun 5, 1977 | EF3 | 82 km | 69.5 mi | 0 |
| Jun 4, 1975 | EF3 | 75 km | 2.3 mi | 0 |
| Apr 21, 1974 | EF3 | 57 km | 22.2 mi | 0 |
| Apr 21, 1974 | EF3 | 53 km | 58.6 mi | 2 |
| Aug 2, 1967 | EF3 | 92 km | 0.1 mi | 2 |
| Jul 19, 1963 | EF3 | 63 km | 10.6 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
8 wildfires (100+ acres) recorded within 100 km. Largest: UNNAMED (1,524 acres, 2006).
| Year | Name | Acres Burned | Distance |
| 2006 | UNNAMED | 1,524 | 49 km |
| 2010 | RX BURN | 1,236 | 49 km |
| 1994 | SOMMERS | 938 | 55 km |
| 1988 | PEACHY RD | 812 | 53 km |
| 2024 | IBSP SOUTH F1 RX | 690 | 92 km |
| 2006 | UNNAMED | 612 | 58 km |
| 2007 | TOWER RD 2 | 592 | 53 km |
| 2024 | RX-HWY Y - SOUTH | 553 | 41 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 19°F (-7°C) | 1.3 in | Coldest |
| February | 23°F (-5°C) | 1.1 in | Driest |
| March | 33°F (1°C) | 2.1 in | |
| April | 45°F (7°C) | 3.2 in | |
| May | 57°F (14°C) | 3.0 in | |
| June | 66°F (19°C) | 3.7 in | |
| July | 72°F (22°C) | 3.9 in | Warmest, Wettest |
| August | 69°F (21°C) | 3.9 in | |
| September | 61°F (16°C) | 3.9 in | |
| October | 50°F (10°C) | 2.5 in | |
| November | 36°F (2°C) | 2.4 in | |
| December | 24°F (-5°C) | 1.8 in |
Merton has a seasonal temperature swing of 53°F / from 19°F in January to 72°F in July. Total annual precipitation is 32.7 inches, with July being the wettest month (3.9") and February the driest (1.1").