Sweetwater County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Sweetwater County: 0.
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.

Every large fire

1. Large fires mapped by the Monitoring Trends in Burn Severity program since 1984: 1,000 acres or more in the West, 500 or more in the East. Prescribed burns are excluded. Acres here are the part of each perimeter inside this place.

Monitoring Trends in Burn Severity (USGS and U.S. Forest Service), 1984 to 2026.

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.

Every earthquake of magnitude 4 or more within 50 miles

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.

Mapped landslides

Mapped by WY WSGS (970), USGS Seismogenic Mass Movements (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. Jul 28, 2021Flash Flood$750,000
   National Weather Service narrative

   Runoff from higher desert terrain and rain falling on an urbanized landscape led to flash flooding across western portions of Rock Springs.

2. Apr 25, 2009Hail$700,000
   National Weather Service narrative

   Golf ball sized hail fell along Interstate 80 from nine miles west of Wamsutter to Wamsutter.

3. Apr 13, 2002Wildfire$261,000
   National Weather Service narrative

   How the fire was started can not be confirmed. After fire started, winds of 50 mph rapidly spread the fire across Superior. Four homes were destroyed, 23 buildings were destroyed, including garages and sheds. Also, 9 vehicles were destroyed. Damage dollar amount was based on information provided by the victims, insurance companies and city officials.

4. Jul 7, 2015Flash Flood$250,000
   National Weather Service narrative

   A second straight day of drenching thunderstorms brought widespread flash flooding throughout the city of Rock Springs. Many businesses and residential basements were flooded. In addition, numerous cars were stranded in flood waters both on city streets and in large parking lots.

5. Aug 17, 2007Flash Flood$250,000
   National Weather Service narrative

   Heavy rainfall on the south side of Green River produced a flash flood. Within 25 minutes, between 1.25 inches and 1.75 inches of rain was measured in this area of town. A fence at the landfill was washed out by a wall of water six feet high. The water and mud caused extensive damage to a scale mechanism at the landfill. Additionally, several basements were flooded, South Hill on State Highway 530 had mud and debris across it, and a pool near one school was completely inundated by mud. Many yards and streets on the south side of Green River were covered with six to eight inches of mud.

6. Apr 14, 2000Tornado$30,000
   National Weather Service narrative

   Weak, short-lived tornado that apparently developed along the gust front associated with a line of fast-moving thunderstorms. James Town is located just west of Green River.

7. Aug 2, 2007Flash Flood$25,000
   National Weather Service narrative

   Monsoon moisture streamed north into Sweetwater County initiating thunderstorms which produced intense rainfall east of Rock Springs. Rainfall of around one inch fell in less than one hour in a small drainage north of Interstate 80. Culverts designed to take run-off under the interstate were unable to keep up with the volume of water. Subsequently, flood waters over-topped the interstate in some spots between mile markers 122 and 125. A frontage road south of the interstate also experienced flooding as culverts were unable to divert water fast enough. Traffic was slowed or stopped at times due to water, mud, and debris on the road surface.

8. Jul 6, 2015Flash Flood$20,000
   National Weather Service narrative

   The Rock Springs Police Department reported flooding in a trailer park on 9th Street near the South Side Belt Route. Up to 3 feet of water collected in low-lying areas of the park and displaced some residents before the water receded shortly after 2100MST. Several media outlets shared pictures of street flooding in and around downtown Rock Springs.

9. Apr 25, 2009Thunderstorm Wind$15,000
   National Weather Service narrative

   Power lines were downed and at least one home under construction was damaged in Wamsutter by strong thunderstorm wind.

10. Oct 16, 2016Winter Storm, Upper Green River Basin$15,000
    National Weather Service narrative

    Heavy snow fell with widespread reports of 6 to 12 inches. At Big Piney, the heavy, wet snow caused the school bus barn's roof to collapse.

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

98°F3 times, most recently Jul 26, 2026

All-time low

−37°FJan 12, 1963

Warmest night

67°FAug 4, 2024

Coldest day

−19°FJan 11, 1963

Wettest day

2.00 inSep 11, 1973

Snowiest day

21.8 inFeb 7, 2001

Hottest year

2025mean 47.5°F

Coldest year

1993mean 39.6°F

Wettest year

196514.54 in

Driest year

20203.11 in

Station Rock Springs Airport (USW00024027), 6,758 ft elevation, 12.9 miles from the population centre. Daily records from 1948 to October 26, 2026; 99.6% 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 USW00024027.
• 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.