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Belmont, California

City in San Mateo County, California

Air quality

The air at Belmont

Index 43, good, led by ozone. Read at 5 PM from its reporting area, Redwood City (CA), 5 miles off.

43Good
  • Fine particles (PM2.5)27Good5.5 mi
  • Ozone43Good49 ppb5.5 mi
  • Nitrogen dioxide10Good11 ppb5.5 mi
  • Sulfur dioxide0Good0.5 ppb20.4 mi
  • Carbon monoxide-0.2 ppm5.5 mi

The days ahead

Good each day through Wed Oct 21, led by ozone. Yesterday measured 46, good.

Smoke, the next 42 hours

Little smoke near the ground through Sun 11 AM: the index from smoke stays at 11 or under.

FriSatSun

Precipitation

What has fallen at Belmont

None in the last 3 days, to Fri 5 PM. 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 Belmont, the next 42 hours

Visibility stays 10 miles or more through Sun 11 AM.

FriSatSun

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

What is measuring near here

The 5 instruments nearest Belmont, how far away each one is, how high it stands, and what kind of measurement it makes. The nearest is 1.0 miles away.

measured now3 instruments

measured daily2 instruments

Belmont 1.1 NECA-SM-29

In a volunteer observer's own ground/1.0 mi away/24 ft/164 ft below here

precip, snowfall, snow depth

Rank-

Redwood CityRWCC1

At a cooperative observer's station/4.1 mi away/16 ft/172 ft below here

snowfall, snow depth, precip, high, low

Rank277of 4,461

Station report

The weather at San Carlos Airport, drawn

The nearest airport reporting now, 2.6 mi from Belmont, California. From its report of Oct 16, 2026, 4:47 PM local time: 3 of its 6 sheets.

The sky

Clear; visibility 10 mi or more.

Section of the sky over San Carlos Airport, height above the station to scale: a clear sky, and visibility of 10 mi or more.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT SQLFIG. A THE SKY OVER SAN CARLOS AIRPORTSECTION, 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 STATIONCLEARVISIBILITY, MILES: 10 MI OR MORE0510TITLESan Carlos Airport, the skySTATION REPORT · ASOS SQLTYPESECTIONSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 1 of 6DATE2026-10-16IDSR-SQL-1DRAWN AS linework on paperSOURCES FB-SKY-001

The air

87.8 F with a dew point of 42.8 F, 21 per cent relative humidity. Air lifted from the station would cool to its dew point, where cloud forms, about 10,200 ft up.

Chart of the air at San Carlos Airport: temperature 87.8 degrees Fahrenheit and dew point 42.8, 21 per cent relative humidity; air lifted from the station cools along the dry rate and meets its dew point about 10,200 feet above the station; height to scale.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT SQLFIG. B THE AIR AT SAN CARLOS AIRPORTTHE REPORTED TEMPERATURE AND DEW POINT, AND AIR LIFTED FROM THE STATION WITHOUT MIXING UNTIL IT SATURATES; HEIGHT ABOVE THE STATION TO SCALEFT ABOVE THE STATION02,0004,0006,0008,00010,00012,00020 F40 F60 F80 F100 FSATURATES 10,200 FT ABOVE THE STATION, AT 33.5 FTEMPERATURE 87.8 FDEW POINT 42.8 FSPREAD 45.0 FRELATIVE HUMIDITY 21 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 POINTTITLESan Carlos Airport, the airSTATION REPORT · ASOS SQLTYPECHARTSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 2 of 6DATE2026-10-16IDSR-SQL-2DRAWN AS linework on paperSOURCES FB-WAT-002, FB-ENG-011, FB-ENG-005

The wind

From the north northwest (340 degrees) at 8 mph: force 3, a gentle breeze on the Beaufort scale.

Plan of the wind at San Carlos Airport, north up: blowing from 340 degrees, the north northwest, at 8 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 SQLFIG. C THE WIND AT SAN CARLOS AIRPORTPLAN, NORTH UP: THE WIND AS REPORTED, AND WHERE IT SITS ON THE BEAUFORT SCALENESWTHE STATIONFROM 340°BEAUFORT FORCELEAST WIND, MPH0CALM01LIGHT AIR12LIGHT BREEZE43GENTLE BREEZE8NOW, 8 MPH4MODERATE BREEZE135FRESH BREEZE196STRONG BREEZE257NEAR GALE328GALE399STRONG GALE4710STORM5511VIOLENT STORM6412HURRICANE FORCE73TITLESan Carlos Airport, the windSTATION REPORT · ASOS SQLTYPEPLAN north upSCALENOT TO SCALEREVAS REPORTED SHEET 3 of 6DATE2026-10-16IDSR-SQL-3DRAWN AS linework on paperSOURCES FB-EVT-150, FB-ENG-008, FB-INS-002

The full report of San Carlos Airport, in 6 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 Belmont

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

Near Belmont

River and lake gauges