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Altadena, California

Community in Los Angeles County, California

Air quality

The air at Altadena

Index 21, good, led by ozone. Read at 5 AM from its reporting area, W San Gabriel Vly (CA), 4 miles off.

21Good
  • Fine particles (PM2.5)-9.9 mi
  • Ozone21Good20 ppb4 mi
  • Coarse particles (PM10)-9.9 mi
  • Nitrogen dioxide14Good15 ppb4 mi
  • Sulfur dioxide0Good0.2 ppb9.9 mi
  • Carbon monoxide-0.4 ppm9.9 mi

The days ahead

Good each day through Today, led by ozone. Yesterday measured 50, good.

Smoke, the next 42 hours

Little smoke near the ground through Sat 11 PM: the index from smoke stays at 6 or under.

FriSat

Precipitation

What has fallen at Altadena

None in the last 3 days, to Fri 5 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 Altadena, the next 42 hours

Visibility stays 10 miles or more through Sat 11 PM.

FriSat

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

What is measuring near here

The 6 instruments nearest Altadena, how far away each one is, how high it stands, and what kind of measurement it makes. The nearest is 0.5 miles away.

measured now4 instruments

measured daily2 instruments

AltadenaADAC1

At a cooperative observer's station/0.5 mi away/1,145 ft/142 ft below here

snowfall, snow depth, precip, high, low

Rank-

Altadena 1.0 WCA-LA-127

In a volunteer observer's own ground/0.9 mi away/1,204 ft/83 ft below here

precip, snowfall, snow depth

Rank-

Station report

The weather at Mount Wilson, drawn

The nearest airport reporting now, 5.1 mi from Altadena, California. From its report of Oct 16, 2026, 5:20 AM local time: 3 of its 5 sheets.

The air

55.4 F with a dew point of 33.8 F, 44 per cent relative humidity. Air lifted from the station would cool to its dew point, where cloud forms, about 4,900 ft up.

Chart of the air at Mount Wilson: temperature 55.4 degrees Fahrenheit and dew point 33.8, 44 per cent relative humidity; air lifted from the station cools along the dry rate and meets its dew point about 4,900 feet above the station; height to scale.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT MWSFIG. B THE AIR AT MOUNT WILSONTHE REPORTED TEMPERATURE AND DEW POINT, AND AIR LIFTED FROM THE STATION WITHOUT MIXING UNTIL IT SATURATES; HEIGHT ABOVE THE STATION TO SCALEFT ABOVE THE STATION01,0002,0003,0004,0005,0006,0007,00020 F30 F40 F50 F60 F70 FSATURATES 4,900 FT ABOVE THE STATION, AT 29.2 FTEMPERATURE 55.4 FDEW POINT 33.8 FSPREAD 21.6 FRELATIVE HUMIDITY 44 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 POINTTITLEMount Wilson, the airSTATION REPORT · ASOS MWSTYPECHARTSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 1 of 5DATE2026-10-16IDSR-MWS-1DRAWN AS linework on paperSOURCES FB-WAT-002, FB-ENG-011, FB-ENG-005

The wind

From the west northwest (300 degrees) at 3 mph, gusting 7 mph: force 1, a light air on the Beaufort scale. The strongest gust today was 14 mph.

Plan of the wind at Mount Wilson, north up: blowing from 300 degrees, the west northwest, at 3 miles an hour, gusting 7; beside it the Beaufort scale from calm to hurricane force, force 1, light air, marked.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT MWSFIG. C THE WIND AT MOUNT WILSONPLAN, NORTH UP: THE WIND AS REPORTED, AND WHERE IT SITS ON THE BEAUFORT SCALENESWTHE STATIONFROM 300°BEAUFORT FORCELEAST WIND, MPH0CALM01LIGHT AIR1NOW, 3 MPH2LIGHT BREEZE4GUST, 7 MPH3GENTLE BREEZE84MODERATE BREEZE135FRESH BREEZE196STRONG BREEZE257NEAR GALE328GALE399STRONG GALE4710STORM5511VIOLENT STORM6412HURRICANE FORCE73TITLEMount Wilson, the windSTATION REPORT · ASOS MWSTYPEPLAN north upSCALENOT TO SCALEREVAS REPORTED SHEET 2 of 5DATE2026-10-16IDSR-MWS-2DRAWN AS linework on paperSOURCES FB-EVT-150, FB-ENG-008, FB-INS-002

The column

At 5,705 ft above sea level, 19 per cent of the atmosphere's air lies below the station. The standard atmosphere puts the pressure there at 24.25 inHg and the temperature at 38.7 F; it reports 55.4 F, 16.7 F warmer than standard.

Section from sea level of where Mount Wilson stands in the atmosphere, height to scale: the station 5,705 feet above sea level with 19 per cent of the air below it; the standard atmosphere's pressure there, 24.25 inches of mercury, and temperature, 38.7 degrees Fahrenheit.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT MWSFIG. D WHERE MOUNT WILSON STANDS IN THE ATMOSPHERESECTION FROM SEA LEVEL, HEIGHT TO SCALE, THE STATION IN THE STANDARD ATMOSPHEREFT ABOVE SEA LEVEL05,00010,00015,000SEA LEVEL, 29.92 inHg IN THE STANDARD ATMOSPHEREMOUNT WILSON19 PER CENT OF THE AIR BELOW IT5,705 FT10 PER CENT OF THE AIR BELOW, 2,890 FT20 PER CENT OF THE AIR BELOW, 6,050 FT30 PER CENT OF THE AIR BELOW, 9,540 FT40 PER CENT OF THE AIR BELOW, 13,470 FTSTANDARD PRESSURE HERE24.25 inHgSTANDARD TEMPERATURE HERE38.7 FTEMPERATURE, REPORTED55.4 FTITLEMount Wilson, the columnSTATION REPORT · ASOS MWSTYPESECTIONSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 3 of 5DATE2026-10-16IDSR-MWS-3DRAWN AS linework on paperSOURCES FB-ENG-001, FB-ENG-003

The full report of Mount Wilson, in 5 sheets, each beside the Field Book plates that explain it

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Snow on the ground

Elsewhere in California

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

Near Altadena

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

Near Altadena

River and lake gauges