Weather & Climate in Merrimac, WI
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Merrimac 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. Annual precipitation totals 39.2 inches. The area receives 42.7 inches of snow annually, making winter weather a significant factor for residents. Air quality is rated Good with a median AQI of 37. 85% of days have good air quality. The city sits at an elevation of 811 feet.
Temperature
19°F Jan (-8°C)
72°F Jul (22°C)
| Annual Average | 47.1°F |
| 13% below US avg | |
| January Average | 19°F (-8°C) |
| July Average | 72°F (22°C) |
Geography
| Elevation | 811 ft (247 m) |
| Area | 1.5 sq mi (3.9 km²) |
| Population Density | 701/sq mi |
| Coordinates | 43.3756°N, 89.6269°W |
| Timezone | America/Chicago |
| County | Sauk County County |
| Nearest Airport | Dane County Regional/Truax Field (MSN) 22 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 37.0 |
| Rating | Good |
| Good Days % | 85.2% |
| Unhealthy Days | 0 |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 72.1 / 100 |
| Social Vulnerability | 21.9 / 100 |
| Community Resilience | 82.6 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively Moderate |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Relatively Low |
| Ice Storm | Relatively Low |
| Drought | Relatively Low |
| Cold Wave | Relatively Moderate |
| Landslide | Relatively Moderate |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Tornado History
530 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 35 fatalities, 711 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 18, 1996 | EF5 | 89 km | 13.3 mi | 0 |
| Jun 7, 1984 | EF5 | 53 km | 36.0 mi | 9 |
| Jul 3, 1983 | EF4 | 61 km | 0.5 mi | 0 |
| Apr 21, 1974 | EF4 | 77 km | 26.0 mi | 0 |
| Apr 19, 1957 | EF4 | 71 km | 21.1 mi | 1 |
| Apr 3, 1956 | EF4 | 81 km | 11.5 mi | 7 |
| Sep 26, 1951 | EF4 | 32 km | 9.0 mi | 1 |
| Aug 7, 2021 | EF3 | 93 km | 9.4 mi | 0 |
| Jun 16, 2014 | EF3 | 42 km | 1.0 mi | 0 |
| Aug 18, 2005 | EF3 | 53 km | 18.6 mi | 1 |
| Jun 23, 2004 | EF3 | 62 km | 33.3 mi | 0 |
| Jun 23, 2004 | EF3 | 64 km | 7.6 mi | 1 |
| Aug 27, 1994 | EF3 | 84 km | 10.5 mi | 2 |
| Aug 29, 1992 | EF3 | 78 km | 28.0 mi | 1 |
| Jun 17, 1992 | EF3 | 56 km | 16.0 mi | 0 |
| Jun 8, 1984 | EF3 | 33 km | 29.0 mi | 0 |
| Jul 3, 1983 | EF3 | 92 km | 1.0 mi | 0 |
| Jun 5, 1980 | EF3 | 75 km | 10.7 mi | 0 |
| Apr 7, 1980 | EF3 | 54 km | 1.2 mi | 0 |
| Jun 5, 1977 | EF3 | 88 km | 69.5 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950-2024, US only).
Wildfire History
20 wildfires (100+ acres) recorded within 100 km. Largest: COTTONVILLE INCIDENT (3,466 acres, 2005).
| Year | Name | Acres Burned | Distance |
| 2005 | COTTONVILLE INCIDENT | 3,466 | 82 km |
| 1987 | BIG BURN | 3,154 | 98 km |
| 1994 | BIG BURN | 2,248 | 97 km |
| 1997 | BIG BURN | 1,642 | 99 km |
| 2004 | POOL ONE NORTH | 1,576 | 88 km |
| 2006 | UNNAMED | 1,524 | 83 km |
| 1998 | UNNAMED | 1,297 | 98 km |
| 2010 | RX BURN | 1,236 | 83 km |
| 2007 | UNNAMED | 981 | 90 km |
| 1994 | SOMMERS | 938 | 80 km |
| 2003 | UNNAMED | 901 | 99 km |
| 1998 | PR 17 | 896 | 89 km |
| 2007 | UNNAMED | 875 | 88 km |
| 2009 | UNNAMED | 867 | 90 km |
| 1988 | PEACHY RD | 812 | 79 km |
| 2007 | PR 16 | 778 | 98 km |
| 2006 | PR 17 RX FIRE | 701 | 98 km |
| 2018 | 2018 BADGER RX BURNS | 659 | 10 km |
| 2005 | UNNAMED | 657 | 92 km |
| 2003 | PR 17 | 632 | 98 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 19°F (-8°C) | 1.5 in | Coldest, Driest |
| February | 22°F (-5°C) | 1.5 in | |
| March | 34°F (1°C) | 2.2 in | |
| April | 46°F (8°C) | 4.0 in | |
| May | 59°F (15°C) | 4.6 in | |
| June | 69°F (20°C) | 5.4 in | Wettest |
| July | 72°F (22°C) | 4.9 in | Warmest |
| August | 70°F (21°C) | 4.4 in | |
| September | 62°F (17°C) | 3.8 in | |
| October | 50°F (10°C) | 3.0 in | |
| November | 37°F (3°C) | 2.3 in | |
| December | 25°F (-4°C) | 1.7 in |
Merrimac has a seasonal temperature swing of 54°F / from 19°F in January to 72°F in July. Total annual precipitation is 39.2 inches, with June being the wettest month (5.4") and January the driest (1.5").