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O'Fallon, Missouri

City in St. Charles County, Missouri

Air quality

The air at O'Fallon

Index 19, good, led by coarse particles. Read at 5 AM from its reporting area, Saint Louis (MO), 10 miles off.

19Good
  • Fine particles (PM2.5)16Good-
  • Ozone17Good12 ppb14 mi
  • Coarse particles (PM10)19Good-
  • Nitrogen dioxide2Good2.4 ppb14.7 mi
  • Sulfur dioxide0Good0.2 ppb14.7 mi

The days ahead

Yesterday measured 18, good.

Smoke, the next 44 hours

No smoke near the ground through Mon 1 AM.

SatSun

Precipitation

What has fallen at O'Fallon

0.01 in in the last 24 hours, 0.57 in over the last 3 days, to Sat 5 AM. Measured by radar and rain gauges, as water.

Last 24 hours
0.01in
Last 3 days
0.57in

Visibility

How far you can see at O'Fallon, the next 44 hours

Visibility stays 9 miles or more through Mon 1 AM, lowest 10 miles Sat 7 AM.

SatSun

On the radar over O'Fallon, MissouriReflectivityStorm topsRain rateRain, last 24 hoursForecast temperatureForecast rain totalEvery picture

What is measuring near here

The 6 instruments nearest O'Fallon, how far away each one is, how high it stands, and what kind of measurement it makes. The nearest is 0.1 miles away.

measured now4 instruments

Citizen station FW9748FW9748

In a volunteer observer's own ground/1.9 mi away/590 ft/4 ft above here

temp, humidity, wind, precip, pressure

Rank-

St. CharlesSCLM7

At a river or reservoir gauge/13.2 mi away/443 ft/143 ft below here

temp, wind, gust, humidity, pressure

Rank561of 1,043

measured daily2 instruments

O Fallon 0.4 WMO-SS-45

In a volunteer observer's own ground/0.1 mi away/609 ft/23 ft above here

precip, snowfall, snow depth

Rank-

Station report

The weather at St. Louis/Spirit, drawn

The nearest airport reporting now, 9.3 mi from O'Fallon, Missouri. From its report of Oct 17, 2026, 5:54 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 St. Louis/Spirit, 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 SUSFIG. A THE SKY OVER ST. LOUIS/SPIRITSECTION, 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 MORE0510TITLESt. Louis/Spirit, the skySTATION REPORT · ASOS SUSTYPESECTIONSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 1 of 6DATE2026-10-17IDSR-SUS-1DRAWN AS linework on paperSOURCES FB-SKY-001

The air

39.0 F with a dew point of 38.0 F, 96 per cent relative humidity. Air lifted from the station would cool to its dew point, where cloud forms, about 200 ft up.

Chart of the air at St. Louis/Spirit: temperature 39.0 degrees Fahrenheit and dew point 38.0, 96 per cent relative humidity; air lifted from the station cools along the dry rate and meets its dew point about 200 feet above the station; height to scale.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT SUSFIG. B THE AIR AT ST. LOUIS/SPIRITTHE REPORTED TEMPERATURE AND DEW POINT, AND AIR LIFTED FROM THE STATION WITHOUT MIXING UNTIL IT SATURATES; HEIGHT ABOVE THE STATION TO SCALEFT ABOVE THE STATION01,0002,0003,00030 F40 F50 FSATURATES 200 FT ABOVE THE STATION, AT 37.7 FTEMPERATURE AND DEW POINT 39.0 F, 38.0 FRELATIVE HUMIDITY 96 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 POINTTITLESt. Louis/Spirit, the airSTATION REPORT · ASOS SUSTYPECHARTSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 2 of 6DATE2026-10-17IDSR-SUS-2DRAWN AS linework on paperSOURCES FB-WAT-020, FB-WAT-002, FB-ENG-011, FB-ENG-005

The wind

From the west southwest (240 degrees) at 3 mph: force 1, a light air on the Beaufort scale.

Plan of the wind at St. Louis/Spirit, north up: blowing from 240 degrees, the west southwest, at 3 miles an hour; beside it the Beaufort scale from calm to hurricane force, force 1, light air, marked.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT SUSFIG. C THE WIND AT ST. LOUIS/SPIRITPLAN, NORTH UP: THE WIND AS REPORTED, AND WHERE IT SITS ON THE BEAUFORT SCALENESWTHE STATIONFROM 240°BEAUFORT FORCELEAST WIND, MPH0CALM01LIGHT AIR1NOW, 3 MPH2LIGHT BREEZE43GENTLE BREEZE84MODERATE BREEZE135FRESH BREEZE196STRONG BREEZE257NEAR GALE328GALE399STRONG GALE4710STORM5511VIOLENT STORM6412HURRICANE FORCE73TITLESt. Louis/Spirit, the windSTATION REPORT · ASOS SUSTYPEPLAN north upSCALENOT TO SCALEREVAS REPORTED SHEET 3 of 6DATE2026-10-17IDSR-SUS-3DRAWN AS linework on paperSOURCES FB-EVT-150, FB-ENG-008, FB-INS-002

The full report of St. Louis/Spirit, in 6 sheets, each beside the Field Book plates that explain it

0in

Snow on the ground

Measured at Dardenne Pr 1 NW (DARM7), 0.7 miles from here, read 16 Oct, 07:00. measured daily

Elsewhere in Missouri

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

Near O'Fallon

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

Near O'Fallon

River and lake gauges