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Alta Sierra, California

Community in Nevada County, California

Air quality

The air at Alta Sierra

Index 21, good, led by ozone. Read at 4 AM from its reporting area, Colfax (CA), 6 miles off.

21Good
  • Fine particles (PM2.5)18Good5.6 mi
  • Ozone21Good24 ppb5.6 mi

The days ahead

Highest 58, moderate, today, led by ozone. Yesterday measured 38, good.

Smoke, the next 44 hours

No smoke near the ground through Sat 11 PM.

FriSat

Precipitation

What has fallen at Alta Sierra

None in the last 3 days, to Fri 3 AM. Measured by radar and rain gauges, as water.

Last 24 hours
0.00in
Last 3 days
0.00in

Visibility

How far you can see at Alta Sierra, the next 44 hours

Visibility stays 10 miles or more through Sat 11 PM.

FriSat

On the radar over Alta Sierra, CaliforniaReflectivityStorm topsRain rateRain, last 24 hoursForecast temperatureForecast rain totalEvery picture

What is measuring near here

The 6 instruments nearest Alta Sierra, how far away each one is, how high it stands, and what kind of measurement it makes. The nearest is 0.8 miles away.

measured now4 instruments

measured daily2 instruments

Grass Valley 6.3 SCA-NV-18

In a volunteer observer's own ground/0.8 mi away/2,125 ft/117 ft below here

precip, snowfall, snow depth

Rank-

Station report

The weather at Grass Valley, drawn

The nearest airport reporting now, 6.9 mi from Alta Sierra, California. From its report of Oct 16, 2026, 3:55 AM local time: 3 of its 6 sheets.

The sky

No cloud below 12,000 ft; visibility 10 mi or more.

Section of the sky over Grass Valley, height above the station to scale: no cloud detected below 12,000 feet, the reach of its ceilometer, and visibility of 10 mi or more.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT GOOFIG. A THE SKY OVER GRASS VALLEYSECTION, HEIGHT ABOVE THE STATION TO SCALE, EACH LAYER AT THE HEIGHT OF ITS BASE AS REPORTED; COVER IN EIGHTHS OF THE SKY; TOPS NOT MEASUREDFT ABOVE THE STATION05001,0001,5002,0002,5003,000ETAGESLOWTHE STATIONTHE CEILOMETER READS TO 12,000 FT, ABOVE THIS SHEETNO CLOUD DETECTED BELOW 12,000 FTVISIBILITY, MILES: 10 MI OR MORE0510TITLEGrass Valley, the skySTATION REPORT · ASOS GOOTYPESECTIONSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 1 of 6DATE2026-10-16IDSR-GOO-1DRAWN AS linework on paperSOURCES FB-SKY-001

The air

71.6 F with a dew point of 14.0 F, 11 per cent relative humidity. Air lifted from the station would cool to its dew point, where cloud forms, about 12,800 ft up.

Chart of the air at Grass Valley: temperature 71.6 degrees Fahrenheit and dew point 14.0, 11 per cent relative humidity; air lifted from the station cools along the dry rate and meets its dew point about 12,800 feet above the station; height to scale.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT GOOFIG. B THE AIR AT GRASS VALLEYTHE REPORTED TEMPERATURE AND DEW POINT, AND AIR LIFTED FROM THE STATION WITHOUT MIXING UNTIL IT SATURATES; HEIGHT ABOVE THE STATION TO SCALEFT ABOVE THE STATION02,0004,0006,0008,00010,00012,00014,00016,000-10 F10 F30 F50 F70 FSATURATES 12,800 FT ABOVE THE STATION, AT 3.2 FTEMPERATURE 71.6 FDEW POINT 14.0 FSPREAD 57.6 FRELATIVE HUMIDITY 11 PER CENTTHE AIR COOLS ABOUT 5.4 F EACH 1,000 FT IT RISES, AND ITS DEW POINT ABOUT 1 FSOLID: THE LIFTED AIR'S TEMPERATURE; DASHED: ITS DEW POINTTITLEGrass Valley, the airSTATION REPORT · ASOS GOOTYPECHARTSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 2 of 6DATE2026-10-16IDSR-GOO-2DRAWN AS linework on paperSOURCES FB-WAT-002, FB-ENG-011, FB-ENG-005

The wind

From the east (80 degrees) at 9 mph: force 3, a gentle breeze on the Beaufort scale.

Plan of the wind at Grass Valley, north up: blowing from 80 degrees, the east, at 9 miles an hour; beside it the Beaufort scale from calm to hurricane force, force 3, gentle breeze, marked.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT GOOFIG. C THE WIND AT GRASS VALLEYPLAN, NORTH UP: THE WIND AS REPORTED, AND WHERE IT SITS ON THE BEAUFORT SCALENESWTHE STATIONFROM 80°BEAUFORT FORCELEAST WIND, MPH0CALM01LIGHT AIR12LIGHT BREEZE43GENTLE BREEZE8NOW, 9 MPH4MODERATE BREEZE135FRESH BREEZE196STRONG BREEZE257NEAR GALE328GALE399STRONG GALE4710STORM5511VIOLENT STORM6412HURRICANE FORCE73TITLEGrass Valley, the windSTATION REPORT · ASOS GOOTYPEPLAN north upSCALENOT TO SCALEREVAS REPORTED SHEET 3 of 6DATE2026-10-16IDSR-GOO-3DRAWN AS linework on paperSOURCES FB-EVT-150, FB-ENG-008, FB-INS-002

The full report of Grass Valley, in 6 sheets, each beside the Field Book plates that explain it

0in

Snow on the ground

Measured at Grass Valley No. 2 (GRAC1), 5.1 miles from here, read 15 Oct, 07:30. measured daily

Elsewhere in California

33 places, each with its own forecast and its own instruments.

Near Alta Sierra

The nearest places, each with its own forecast and the instruments nearest it.

Near Alta Sierra

River and lake gauges