Grass Valley

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond this area.
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.

Flood insurance figures are for Nevada County, the county that contains Grass Valley.

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 in Nevada County, the county that contains Grass Valley.

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.

The drought index is for Nevada County, the county that contains Grass Valley.

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 city centre.
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.

Volcanoes within 100 miles

1. U.S. volcanoes within 100 miles, from the USGS Volcano Hazards Program. The threat category is the USGS 2018 National Volcanic Threat Assessment, which ranks volcanoes by how hazardous their past eruptions were and how many people and how much infrastructure lie near them. It is not a forecast of eruption.

USGS Volcano Hazards Program, retrieved October 30, 2026.

Mapped landslides

Landslides mapped in Nevada County.

Mapped by NASA (14).

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. Jun 24, 2007Wildfire, Greater Lake Tahoe Area$500 million
   National Weather Service narrative

   The human-caused Angora wildfire started on June 24th and continued to burn through the end of June. Strong winds gusting to 40 mph caused the wildfire to spread across 3,100 acres south of Lake Tahoe. A total of 254 houses and over 60 commercial structures were destroyed.

2. Feb 8, 2017Flood$3.6 million
   National Weather Service narrative

   HWY 49 was closed north of Nevada City, from Newtown Rd. to Tyler Foote Rd. due to multiple slip outs.

3. Jan 10, 2017Debris Flow$1.1 million
   National Weather Service narrative

   Rocks, mud, and a tree across the roadway on Highway 49. The roadway was unpassable due to numerous slides on both sides of the South Yuba River Bridge.

4. Dec 31, 2005Flood$1.0 million
   National Weather Service narrative

   Interstate 80 was closed because of a large mudslide approximately 5 miles east of Truckee. The mudslide occurred at around 3 am on December 31st, blocking both directions on the Interstate. California Highway 89 was also closed due to a mudslide. Donner Creek caused flooding of some buildings in Truckee. This was the second largest flood of record on Donner Creek. California Highway 89 was closed across Nevada County from Truckee to the Sierra County line.

5. Apr 15, 2002Heavy Snow, Greater Lake Tahoe Area$500,000
   National Weather Service narrative

   A heavy snow shower, creating low visibilityand a slick roadway, caused a 21 vehicle pile-up on Intertstate 80 about 5 miles east of Truckee, CA. Several trucks were involved in the accident with at least one semi trailer destroyed.

6. Jan 8, 2017Debris Flow$480,000
   National Weather Service narrative

   A large mudslide near the Donner Lake Interchange on Interstate 80 caused the closure of the freeway. The westbound lanes closed at 1802PST, followed by the eastbound lanes (downed power lines) at 1918PST. The road was completely closed between Kingvale and Truckee until 0520PST on the 9th when it was opened for local traffic and law enforcement. The freeway was fully opened at 1040PST on the 9th. The damage estimate was obtained from a preliminary damage assessment from CALTRANS.

7. Jan 9, 2017Debris Flow$480,000
   National Weather Service narrative

   Interstate 80 was closed in both directions over the Sierra Nevada near Donner Lake. CalTrans and CHP reported a 60 foot mudslide at 6 pm due to a mudslide. Interstate 80 was shut down for 17 hours west bound, 14 hours east bound, until CalTrans removed the debris.

8. Dec 17, 2010Winter Storm, Greater Lake Tahoe Area$400,000
   National Weather Service narrative

   Ski resorts accumulated an average of 5 to 8 feet of snow. Twenty to 30 inches of snow fell north and west of Lake Tahoe below 7000 feet. However, valley areas south and east of Lake Tahoe received as little as 12 inches with periods of rain. Heavy wet snow caused a rock slide on highway 50 which closed the road on the 19th. In addition to snow, numerous reports of downed trees and associated damage were noted on the 19th. Falling trees were responsible for one destroyed house in South Lake Tahoe, with winds gusting to 63 mph and 68 mph in Truckee and South Lake Tahoe, respectively, and up to 155 mph over the crest. Finally, a tree fell on a ski lift cable at the Sierra-at-Tahoe…

9. Nov 7, 2002High Wind, Greater Lake Tahoe Area$300,000
   National Weather Service narrative

   Wind gusts estimated at over 80 mph blew down trees in the South Lake Tahoe, CA area. Falling trees severely damaged one home and two vehicles. Tree limbs damaged four other homes and downed several power lines, causing scattered power outages. Sparking electric lines caused two brush fires, the largest of which scorched 30 acres.

10. Dec 14, 2002High Wind, Greater Lake Tahoe Area$220,000
    National Weather Service narrative

    A strong cold front moving through northern California on December 14 brought near-record nigh winds to northeast California and western Nevada. Wind gusts reports in the 60-80 mph range were common throughout the day across the entire region, with a few gusts near 100 mph. Remote wind sensors along the Sierra Crest measured wind gusts in excess of 130 mph. Strongest winds occurred just before the cold front moved into the area at about 5:30 p.m. Literally hundreds of trees and thousands of tree limbs were blown down across the region. In addition, there was widespread damage to roofs, fences, commercial billboards and signs, and power lines. Numerous power outages occurred, some…

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°F4 times, most recently Sep 7, 2022

All-time low

3°F2 times, most recently Dec 10, 1972

Warmest night

78°FAug 17, 2020

Coldest day

31°F4 times, most recently Jan 10, 2011

Wettest day

9.05 inOct 25, 2021

Snowiest day

12.0 inJan 6, 1974

Hottest year

2014mean 58.6°F

Coldest year

1982mean 53.0°F

Wettest year

198394.42 in

Driest year

201316.50 in

Snowiest season

27.1 in1971-72

Station Grass Valley #2 (USC00043573), 2,400 ft elevation, 1.4 miles from the city centre. Daily records from 1966 to October 27, 2026; 96.5% 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.

Declarations for Nevada County.

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.

• 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 USC00043573.
• 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.
• Volcanoes USGS Volcano Hazards Program, U.S. volcanoes and 2018 threat assessment.
• 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.