Jefferson County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Jefferson County: 3.
2. Weak tornadoes were under-recorded before Doppler radar coverage became national in the early 1990s, so earlier decades read low. Ratings use the Fujita scale before February 2007 and the Enhanced Fujita scale after.

Storm Prediction Center severe weather database, 1950 to 2025.

Smoke overhead

1. A smoke day is a date on which a smoke plume traced by NOAA Hazard Mapping System analysts from satellite imagery covered this place's point (the county's population centre or the city centre). Counts here are of medium or heavy smoke. Since 2018 analysts have often drawn light smoke as one area over most of the continent, so light-smoke counts are not comparable from year to year. The plumes show smoke anywhere in the air above, not air quality at the ground, and smoke hidden by cloud is missed.

NOAA Hazard Mapping System smoke analysis, 2011 to 2026, retrieved October 30, 2026.

Claims by ZIP code

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026. NOAA Storm Events through 2026.

River crests

River gauges

1. Crests are the highest and the recent crests the National Weather Service lists for each river gauge in the county that has a flood stage, not every flood. Flood categories use each gauge's current flood stages; crests from before levees, dams or channel changes may not be comparable. Crests measured on an old datum are left out of the rankings.

NOAA National Water Prediction Service gauge records, retrieved October 30, 2026.

1. The Palmer Drought Severity Index is computed by NOAA each month from the county's average temperature and precipitation, relative to the county's own climate. Zero is normal; -3 or lower is severe drought and -4 or lower extreme drought. It describes the long-term balance of moisture, not water supply or crop losses.

NOAA NCEI nClimDiv county Palmer Drought Severity Index, 1895 to September 2026, issued October 6, 2026.

1. Earthquakes of magnitude 2.5 or more in the USGS Comprehensive Catalog since 1900. Within 50 miles means the epicentre lies within 50 miles of the county boundary (or inside the county).
2. Small earthquakes were under-recorded before the modern seismic networks of the 1970s and are still missed in remote areas, so early decades read low. Magnitudes are as the catalogue reports them and mix scales (moment, local and body-wave).

USGS ANSS Comprehensive Earthquake Catalog, 1900 to present, retrieved October 30, 2026.

More event types since 1996

Costliest events since 1996

1. Jun 8, 2008Flash Flood$102 million
   National Weather Service narrative

   Heavy rains resulted in flash flooding across much of Jefferson County. Water depths on road surfaces reached 3 feet or more and there were gravel washouts. The rain on June 12th ultimately lead to record-setting crests on the Rock and Crawfish Rivers, and many farm fields remained flooded into early July. The cities of Watertown, Jefferson, and Ft. Atkinson were hard hit by high river levels. The breakdown on residential home damage losses were: 100 with minor damage, 400 with major damage, and 10 destroyed (total of about $36 million). Business losses totaled abouit $21.4 million. Crops losses were estimated at $35 million. Public sector damage was about $44.811 million. There…

2. Apr 13, 2006Hail$4.4 million
   National Weather Service narrative

   Hail sizes ranged from 1.00 to 2.50 inches in diameter.

3. Apr 13, 2006Hail$4.4 million
   National Weather Service narrative

   Wild weather occurred over parts of south-central and southeast Wisconsin on April 13, 2005. Wisconsin's most-costly hailstorm pummeled a large swath from around Mineral Point (Iowa Co.) to north of Milwaukee (Milwaukee Co.), while hurricane-force thunderstorm winds raked parts of Fond du Lac and Sheboygan Counties. Here's what happened: scattered supercells developed in eastern Iowa during the late afternoon hours of April 13th and pushed east-northeastward through southern Wisconsin and northern Illinois during the evening. Three main hailstorms affected southern Wisconsin. The first hailstorm left a swath of hail and hail damage from southern Iowa County (around 1945CST),…

4. Apr 13, 2006Hail$4.4 million
   National Weather Service narrative

   Wild weather occurred over parts of south-central and southeast Wisconsin on April 13, 2005. Wisconsin's most-costly hailstorm pummeled a large swath from around Mineral Point (Iowa Co.) to north of Milwaukee (Milwaukee Co.), while hurricane-force thunderstorm winds raked parts of Fond du Lac and Sheboygan Counties. Here's what happened: scattered supercells developed in eastern Iowa during the late afternoon hours of April 13th and pushed east-northeastward through southern Wisconsin and northern Illinois during the evening. Three main hailstorms affected southern Wisconsin. The first hailstorm left a swath of hail and hail damage from southern Iowa County (around 1945CST),…

5. May 31, 1998Thunderstorm Wind$2.7 million
   National Weather Service narrative

   During the early morning hours of Sunday, May 31st, southcentral and southeast Wisconsin experienced an unprecedented, widespread downburst wind event known as a "derecho." Incredibly powerful, hurricane-force straight-line winds, with peak gusts of 100 to 128 mph tore through 12 counties in this part of the state, while another 8 counties had peak gusts of 60 to 80 mph. Residents noted that the strongest winds only lasted a minute or two, but gusty winds hung on for 15 to 30 minutes. Meteorologically, a solid squall line developed in southern Minnesota and gathered strength as it raced east with a translational speed of 50 to 60 mph across southcentral and southeast Wisconsin.…

6. Jun 1, 2004Flood, Jefferson$2.6 million
   National Weather Service narrative

   Scattered to widespread heavy rains across south-central and southeast Wisconsin during the period of June 9-12, 2004 kept many rivers and streams at or above flood stage for a good part, or most of the month. Monthly rainfall totals generally ranged from 4 to 7 inches across south-central and southeast Wisconsin, with some scattered spots in Sauk, Columbia, Dodge, Walworth, Racine, and Kenosha Counties picking up 7 to 9.5 inches, or 50 to 100% above normal. In some cases, stretches of some rivers actually went above flood stage in May, 2004. Refer to flood and flash flood events in May, 2004, for additional information. During June, 2004, the high water levels kept much of the…

7. Aug 17, 2018Flash Flood$943,000
   National Weather Service narrative

   Approximately 100 911 calls related to flash flooding in Watertown. Numerous streets in Watertown flooded and closed. Some neighborhoods completely flooded with streets, yards, and driveways filled with water. Basement flooding common. A portion of Jefferson Rd. washed out at the bridge where a creek flows into the nearby Rock River. Other road damage or washouts as well. Three vehicle water rescues involving 4 citizens performed by the fire department. A section of track ballast was washed away compromising the railroad ties and tracks. The flooding caused a sanitary sewer overflow/bypass around 10 AM. Additional street flooding and basement flooding in Waterloo, Ixonia, and…

8. Nov 10, 1998High Wind, Jefferson$900,000
   National Weather Service narrative

   Screaming high winds raked all of southcentral and southeast Wisconsin's counties for about 17 hours, resulting in widespread damage to thousands of trees, homes, businesses, power poles, power lines, street lights, road signs, billboards, fences, flagpoles, barns, sheds, crops, boats, cars, trucks, campers, trains, airport hangers, and airplanes. Four people were killed, and 14 people were injured. Estimated monetary damages were $10.31 million to property and $1.625 million to crops. The sustained southwesterly winds of 30 to 40 mph gusted to 60 to 70 mph, with isolated locations having gusts to around 80 mph. These relentless winds eventually caused about 125,000 customers to…

9. Sep 19, 1997Tornado$650,000
   National Weather Service narrative

   Severe thunderstorm winds were responsible for scattered tree and power line damage. Hardest hit was Walworth county were a barn was blown off it's foundation near Sharon (Walworth Co) and another out-building damaged. Several other homes around the county experienced expensive lightning damage due to fires. The 911 center in Elkhorn (Walworth Co) was temporarily disabled when lightning destroyed the communications center, forcing the use of a backup system. In addition, lightning struck and injured a woman in Elkhorn as the storms rolled through that city. Heavy rains of 3 to 4 inches caused urban street flooding on the west side of Monroe in Green county with other incidences of…

10. Jun 21, 2010Tornado$620,000
    National Weather Service narrative

    An EF1 tornado developed in Busseyville just south of the intersection of Draves Road and Loga Road, and moved northeast about 1.3 miles and dissipated at the intersection of STH 106 and Carcajou Rd. Thirty residential structures were minimally affected, 1 had minor damage , and 2 sustained major damage (one of which had a large tree collapse part of the structure). A vehicle was damaged when a large tree branch fell on it. Total private sector damage was estimated at $620,000, which included $590,000 for residential structures, $25,000 for farm buildings, and $5,000 for the damaged vehicle. Uprooted trees and snapped tree limbs were noted along the path of the tornado. Some crop…

1. Storm Events records before 1996 cover only tornadoes, thunderstorm wind and hail. Damage figures are as reported by the National Weather Service at the time, not adjusted for inflation.

NOAA NCEI Storm Events Database, 1950 to 2026, issued October 26, 2026.

All-time high

110°FJul 14, 1936

All-time low

−33°FJan 30, 1951

Warmest night

85°FJul 11, 1921

Coldest day

−12°F3 times, most recently Jan 31, 2019

Wettest day

5.59 inAug 19, 2007

Snowiest day

16.0 inJan 30, 1947

Hottest year

2012mean 51.1°F

Coldest year

1917mean 42.8°F

Wettest year

201849.23 in

Driest year

195822.29 in

Snowiest season

85.7 in2007-08

Station Lake Mills Wwtp (USC00474482), 811 ft elevation, 6.3 miles from the population centre. Daily records from 1893 to October 23, 2026; 90.6% of days in the last 30 years are complete. Records at a single station can differ from a city’s official threaded record, which may combine several stations.

NOAA NCEI Global Historical Climatology Network Daily.

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA Disaster Declarations Summaries, retrieved October 30, 2026. Statewide declarations are not listed.

Neighbouring counties

• Tornadoes NOAA Storm Prediction Center severe weather database, through 2025.
• Tropical cyclones NOAA National Hurricane Center HURDAT2 (Atlantic; Northeast and Central Pacific), through 2025.
• Wildfire USGS/USFS Monitoring Trends in Burn Severity, through 2026.
• Storm events NOAA NCEI Storm Events Database, through 2026.
• Flood insurance OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026.
• Declarations OpenFEMA Disaster Declarations Summaries v2, retrieved October 30, 2026.
• Weather records NOAA NCEI Global Historical Climatology Network Daily, station USC00474482.
• River crests NOAA National Weather Service, National Water Prediction Service river gauges, retrieved October 30, 2026.
• Drought NOAA NCEI nClimDiv county Palmer Drought Severity Index, through September 2026.
• Smoke NOAA NESDIS Hazard Mapping System smoke analysis, retrieved October 30, 2026.
• Earthquakes USGS ANSS Comprehensive Earthquake Catalog (ComCat), retrieved October 30, 2026.

Joins, thresholds and known limits are set out in the methodology. Found an error? Report it. Page built October 30, 2026.