San Juan County

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.

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.

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 CO GS (853), NASA (2), USGS Conterminous (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 27, 1999Flash Flood$10,000
   National Weather Service narrative

   Flash flooding covered over a hundred feet of the Durango and Silverton Narrow Gauge Railroad track with 15 feet of mud, logs, and rocks. A section of track and foundation were damaged. Crews worked around the clock for two days to remove the debris and repair the track.

2. Jul 30, 2021Debris Flow$10,000
   National Weather Service narrative

   A section of Hotel Draw Road (Forest Service Road 550) was blocked by a mudslide one-half mile east of its intersection with the Colorado Trail.

3. Jul 23, 2021Debris Flow$10,000
   National Weather Service narrative

   Numerous mudslides occurred in remote areas of San Juan County, most notably at Stony Pass near Pole Creek. Backcountry roads were closed due to cleanup operations.

4. Jun 21, 2024Debris Flow$5,000
   National Weather Service narrative

   Heavy rain from thunderstorms occurred in the early morning hours of June 21 and caused a major rock slide that damaged part of the railroad track for the Durango to Silverton Narrow Gauge Railroad. Exact time of occurrence is estimated. Part of the 45-mile long railroad track was blocked by a pile of debris after a rock slide occurred. Officials were notified about the rock slide just after 7:30 a.m. MDT that morning. The rock slide happened near mile post 486 just outside Needleton, which is about 55 minutes south of Silverton by train.

5. Jul 21, 2007Flash Flood$5,000
   National Weather Service narrative

   Heavy convective rainfall concentrated just north of the La Plata and San Juan County line produced a massive flow of water, rock, and mud which traveled across the Durango to Silverton Narrow Gage Railroad track and dammed up the Animas River about one mile north of Needleton. Initially, the entire river channel was dammed. The river bed at that location was raised 8 feet on the east side of the channel and remained blocked on the west side of the channel. The debris flow covered about 250 feet of railroad track. The peak depth of debris on the railroad track was measured at close to 45 feet. The railroad track did not sustain significant damage, because the lowest several feet…

6. Aug 2, 2011Flash Flood$5,000
   National Weather Service narrative

   A major flash flood roared down from the west slope of the Animas River Valley across the Durango and Silverton Narrow Gauge Railroad and into the Animas River. The flash flood deposited mud, boulders, and pine trees up to 15 feet deep onto a 300 foot section of railroad tracks. The Animas River was also clogged from the debris. It took 6 days for crews to clear the debris and repair the railroad tracks before the railroad could reopen.

7. Aug 2, 2021Debris Flow$2,500
   National Weather Service narrative

   A mudslide closed Hotel Draw Road (Forest Service Road 550) half a mile east of its intersection with the Colorado Trail.

8. Aug 27, 1999Flash Flood$2,000
   National Weather Service narrative

   A flash flood came down across a section of the Durango and Silverton Narrow Gauge Railroad tracks and washed away much of the ballast.

9. Aug 25, 1997Flash Flood$1,000
   National Weather Service narrative

   Heavy rains caused a flash flood which washed out a road near Gladstone.

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

96°FJun 26, 1929

All-time low

−39°FFeb 1, 1985

Warmest night

58°FJul 26, 1920

Coldest day

−14°FDec 15, 1906

Wettest day

4.05 inOct 5, 1911

Snowiest day

27.8 inJan 28, 2008

Hottest year

1934mean 38.1°F

Coldest year

1912mean 31.8°F

Wettest year

191144.78 in

Driest year

195611.33 in

Snowiest season

299.9 in1951-52

Station Silverton (USC00057656), 9,285 ft elevation, 0.7 miles from the population centre. Daily records from 1904 to April 30, 2026; 89.1% 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 USC00057656.
• 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.