Olmsted County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Olmsted County: 1.
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.

Mapped landslides

Mapped by USGS MN (223), NASA (1).

1. Landslides mapped in the USGS compilation of landslide inventories across the United States (version 3.0, 2025), rated probable or better. The compilation joins inventories made by federal and state agencies for different purposes and areas, so the number mapped in a county reflects how closely it has been surveyed as much as how often its slopes fail. An area with few records may simply not have been mapped. Deaths are as recorded in the inventories; a slide listed in two inventories is counted once.

USGS Landslide Inventories across the United States, version 3.0, retrieved October 27, 2026.

More event types since 1996

Costliest events since 1996

1. Aug 18, 2007Flash Flood$35.0 million
   National Weather Service narrative

   Heavy thunderstorm rains caused widespread flash flooding in Rochester and surrounding areas across the county. Extensive damage was caused to sewer systems, water wells, roadways, parks, and flood control reservoirs.||Highway 14 was closed east of Rochester due to wash outs and flash flooding. A mudslide hit the Ronald McDonald house in Rochester with evacuations around 6 a.m. Red Cross shelters were set up. Flooding reports began around 915 p.m. Saturday August 18.

2. Aug 18, 2007Flash Flood$9.6 million
   National Weather Service narrative

   Numerous streets were flooded. Sand bagging was needed with some street closures. Several nearby bridges were badly damaged and railroad tracks were bent out of place. Highway 14 was closed at Highway 42 due to flooding and residents of the Eyota trailer park were evacuated.||In Eyota specifically, 16 of 20 business had damage, 600 of 716 homes had at least water damage, and in most basements there was 18 inches to 5 feet of water.

3. Apr 17, 2026Tornado$8.2 million
   National Weather Service narrative

   This strong EF-2 tornado began on the northeast side of Stewartville resulting in damage to several homes. The tornado then moved northeast through rural areas of Olmsted County while being highly visible on MNDOT cameras and from Rochester. This tornado eventually crossed I-90, hitting a semi-trailer and injuring the occupant, before moving northwest of Simpson. A farmstead near Simpson took a direct hit from the tornado where a single-wide manufactured home was rolled and farm outbuildings were destroyed. The tornado continued northeast into a neighborhood along Marion Road where several homes were rendered uninhabitable due to a collapse of their exterior walls and roof.…

4. Sep 24, 2010Flash Flood$7.0 million
   National Weather Service narrative

   The approach on the north side of the County Road 18 bridge going through Oronoco washed out as the Middle Fork of the Zumbro River flooded. The Lake Shady Dam was also damaged.

5. Sep 23, 2010Flood$3.5 million
   National Weather Service narrative

   Flooding occurred on most of the rivers, streams, and creeks throughout the county. Water caused at least 20 road closures throughout the county, which included U.S. Highway 52 north of Oronoco as well as County Roads 105, 14, 31, 18, 5 and 133. Seven of the roads were damaged, 3 of which saw extensive damage. Two vehicles tried driving across a water covered road in Oronoco and were swept away. The people in the vehicles were rescued safely. Across the county, 81 homes incurred major damage, while 10 homes had minor damage. Of those 91 homes with damage, 50 occurred in the city of Oronoco. In the city of Eyota, the sewer system was full and many homes had water in their…

6. Jun 17, 2010Tornado$1.9 million
   National Weather Service narrative

   An EF1 tornado produced intermittent damage starting near 50th Ave NW just south of the Northern Hills Golf Course northeast almost to the intersection of 55th St NW and and 23rd Ave NW in the city of Rochester. The path of the tornado took it through a residential area where several homes were damaged. It also struck a Menards store doing extensive damage before dissipating a few minutes later. According to media reports, the tornado damaged at least 30 homes, one of which was destroyed.

7. Jul 21, 2005Lightning$1.6 million
   National Weather Service narrative

   Lightning caused a fire, which completely destroyed a home in rural Byron. There were no injuries or deaths reported.

8. Aug 9, 1999Hail$1.5 million
   National Weather Service narrative

   Hail ranging in size from dimes to tennis balls caused considerable damage. Hardest hit was the city of Rochester, where damage to vehicles and homes was estimated in the millions.

9. Aug 9, 1999Hail$1.3 million
   National Weather Service narrative

   Hail ranging in size from dimes to tennis balls caused considerable damage. Hardest hit was the city of Rochester, where damage to vehicles and homes was estimated in the millions.

10. Aug 9, 1999Hail$1.0 million
    National Weather Service narrative

    Hail ranging in size from dimes to tennis balls caused considerable damage. Hardest hit was the city of Rochester, where damage to vehicles and homes was estimated in the millions.

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

108°FJul 14, 1936

All-time low

−40°FJan 30, 1951

Warmest night

85°FJul 3, 1911

Coldest day

−22°FJan 6, 1912

Wettest day

7.47 inJul 11, 1981

Snowiest day

19.8 inMar 18, 2005

Hottest year

2012mean 50.3°F

Coldest year

1917mean 40.6°F

Wettest year

201955.16 in

Driest year

191011.86 in

Snowiest season

86.8 in2018-19

Station Rochester International Airport (USW00014925), 1,306 ft elevation, 8.4 miles from the population centre. Daily records from 1893 to October 26, 2026; 100.0% 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 USW00014925.
• 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.
• Landslides USGS Landslide Inventories across the United States, version 3.0 (2025).
• 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.