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San Mateo, California

City in San Mateo County, California

Air quality

The air at San Mateo

Index 48, good, led by fine particles. Read at 8 PM from its reporting area, Redwood City (CA), 7 miles off.

48Good
  • Fine particles (PM2.5)48Good8 mi
  • Ozone6Good9 ppb8 mi
  • Nitrogen dioxide28Good30 ppb8 mi
  • Sulfur dioxide0Good0.4 ppb17.7 mi
  • Carbon monoxide-0.6 ppm8 mi

The days ahead

Good each day through Tue Oct 20, led by ozone. Yesterday measured 40, good.

Smoke, the next 45 hours

Little smoke near the ground through Sat 5 PM: the index from smoke stays at 11 or under.

FriSat

Precipitation

What has fallen at San Mateo

None in the last 3 days, to Thu 8 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 San Mateo, the next 45 hours

Visibility stays 10 miles or more through Sat 5 PM.

FriSat

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

What is measuring near here

The 5 instruments nearest San Mateo, how far away each one is, how high it stands, and what kind of measurement it makes. The nearest is 0.2 miles away.

measured now3 instruments

measured daily2 instruments

Redwood CityRWCC1

At a cooperative observer's station/6.9 mi away/16 ft/5 ft above here

snowfall, snow depth, precip, high, low

Rank291of 4,465

Station report

The weather at San Carlos Airport, drawn

The nearest airport reporting now, 4.7 mi from San Mateo, California. From its report of Oct 15, 2026, 9:15 PM local time: 3 of its 6 sheets.

The sky

No cloud reported; visibility 10 mi or more.

Section of the sky over San Carlos Airport, height above the station to scale: no cloud reported, 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 STATIONTHE CEILOMETER READS TO 12,000 FT, ABOVE THIS SHEETNO CLOUD REPORTEDVISIBILITY, 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

69.8 F with a dew point of 44.6 F, 40 per cent relative humidity. Air lifted from the station would cool to its dew point, where cloud forms, about 5,800 ft up.

Chart of the air at San Carlos Airport: temperature 69.8 degrees Fahrenheit and dew point 44.6, 40 per cent relative humidity; air lifted from the station cools along the dry rate and meets its dew point about 5,800 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 STATION01,0002,0003,0004,0005,0006,0007,0008,00030 F40 F50 F60 F70 F80 FSATURATES 5,800 FT ABOVE THE STATION, AT 39.1 FTEMPERATURE 69.8 FDEW POINT 44.6 FSPREAD 25.2 FRELATIVE HUMIDITY 40 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

Calm.

Plan of the wind at San Carlos Airport, north up: calm; beside it the Beaufort scale from calm to hurricane force, force 0, calm, 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 STATIONCALMBEAUFORT FORCELEAST WIND, MPH0CALM0NOW, 0 MPH1LIGHT AIR12LIGHT BREEZE43GENTLE BREEZE84MODERATE 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 San Mateo

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

Near San Mateo

River and lake gauges