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O'Fallon, Illinois

City in St. Clair County, Illinois

Air quality

The air at O'Fallon

Index 25, good, led by ozone. Read at 10 PM from its reporting area, St. Louis (Metro-east) (IL), 3 miles off.

25Good
  • Fine particles (PM2.5)18Good15.1 mi
  • Ozone25Good29 ppb15.5 mi
  • Coarse particles (PM10)7Good15.1 mi
  • Nitrogen dioxide3Good3.3 ppb15.5 mi
  • Sulfur dioxide0Good0.8 ppb15.5 mi
  • Carbon monoxide-0.1 ppm15.5 mi

The days ahead

Highest moderate, today, led by fine particles. Yesterday measured 39, good.

Smoke, the next 46 hours

No smoke near the ground through Sat 7 PM.

FriSat

Precipitation

What has fallen at O'Fallon

0.32 in in the last 24 hours, 1.05 in over the last 3 days, to Thu 9 PM. Measured by radar and rain gauges, as water.

Last 24 hours
0.32in
Last 3 days
1.05in

Visibility

How far you can see at O'Fallon, the next 46 hours

Visibility stays 4 miles or more through Sat 7 PM, lowest 5 miles Fri 2 PM.

FriSat

On the radar over O'Fallon, IllinoisReflectivityStorm 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 0.7 miles away.

measured now4 instruments

measured daily2 instruments

O Fallon 1.3 NNWIL-SC-30

In a volunteer observer's own ground/0.7 mi away/553 ft/24 ft above here

precip, snowfall, snow depth

Rank-

Station report

The weather at Belleville - Scott AFB, drawn

The nearest airport reporting now, 5.1 mi from O'Fallon, Illinois. From its report of Oct 15, 2026, 9:55 PM local time: 3 of its 6 sheets.

The sky

Scattered at 8,000 ft, broken at 19,000 ft; the ceiling is 19,000 ft; visibility 10 mi or more.

Section of the sky over Belleville - Scott AFB, height above the station to scale: scattered cloud with its base at 8,000 feet, broken cloud with its base at 19,000 feet, the ceiling at 19,000 feet, and visibility of 10 mi or more.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT BLVFIG. A THE SKY OVER BELLEVILLE - SCOTT AFBSECTION, 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 STATION05,00010,00015,00020,00025,00030,000ETAGESLOWMIDDLEHIGHTHE STATIONBKN 19,000 FTBROKEN, 5 TO 7 EIGHTHS OF THE SKYSCT 8,000 FTSCATTERED, 3 TO 4 EIGHTHS OF THE SKYCEILING 19,000 FTVISIBILITY, MILES: 10 MI OR MORE0510TITLEBelleville - Scott AFB, the skySTATION REPORT · ASOS BLVTYPESECTIONSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 1 of 6DATE2026-10-16IDSR-BLV-1DRAWN AS linework on paperSOURCES FB-SKY-001, FB-SKY-013, FB-SKY-014, FB-SKY-010, FB-SKY-011, FB-SKY-012

The air

74.0 F with a dew point of 71.8 F, 93 per cent relative humidity. Air lifted from the station would cool to its dew point, where cloud forms, about 500 ft up; the lowest cloud reported is at 8,000 ft.

Chart of the air at Belleville - Scott AFB: temperature 74.0 degrees Fahrenheit and dew point 71.8, 93 per cent relative humidity; air lifted from the station cools along the dry rate and meets its dew point about 500 feet above the station, against the lowest cloud reported at 8,000 feet; height to scale.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT BLVFIG. B THE AIR AT BELLEVILLE - SCOTT AFBTHE REPORTED TEMPERATURE AND DEW POINT, AND AIR LIFTED FROM THE STATION WITHOUT MIXING UNTIL IT SATURATES; HEIGHT ABOVE THE STATION TO SCALEFT ABOVE THE STATION01,0002,0003,0004,00060 F70 F80 FSATURATES 500 FT ABOVE THE STATION, AT 71.2 FABOVE THIS SHEET: LOWEST CLOUD REPORTED, SCT 8,000 FTTEMPERATURE AND DEW POINT 74.0 F, 71.8 FRELATIVE HUMIDITY 93 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 POINTTITLEBelleville - Scott AFB, the airSTATION REPORT · ASOS BLVTYPECHARTSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 2 of 6DATE2026-10-16IDSR-BLV-2DRAWN AS linework on paperSOURCES FB-WAT-020, FB-WAT-002, FB-ENG-011, FB-ENG-005

The wind

From the southwest (230 degrees) at 7 mph: force 2, a light breeze on the Beaufort scale.

Plan of the wind at Belleville - Scott AFB, north up: blowing from 230 degrees, the southwest, at 7 miles an hour; beside it the Beaufort scale from calm to hurricane force, force 2, light breeze, marked.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT BLVFIG. C THE WIND AT BELLEVILLE - SCOTT AFBPLAN, NORTH UP: THE WIND AS REPORTED, AND WHERE IT SITS ON THE BEAUFORT SCALENESWTHE STATIONFROM 230°BEAUFORT FORCELEAST WIND, MPH0CALM01LIGHT AIR12LIGHT BREEZE4NOW, 7 MPH3GENTLE BREEZE84MODERATE BREEZE135FRESH BREEZE196STRONG BREEZE257NEAR GALE328GALE399STRONG GALE4710STORM5511VIOLENT STORM6412HURRICANE FORCE73TITLEBelleville - Scott AFB, the windSTATION REPORT · ASOS BLVTYPEPLAN north upSCALENOT TO SCALEREVAS REPORTED SHEET 3 of 6DATE2026-10-16IDSR-BLV-3DRAWN AS linework on paperSOURCES FB-EVT-150, FB-ENG-008, FB-INS-002

The full report of Belleville - Scott AFB, in 6 sheets, each beside the Field Book plates that explain it

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Snow on the ground

Elsewhere in Illinois

23 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