Mount Vernon, Illinois Air Quality

An Air Quality Alert is issued by the National Weather Service on behalf of a state or local agency when pollution is expected to reach a level that harms health. An Air Stagnation Advisory means the air will not move enough to clear what is already in it.

None are in force near Mount Vernon right now. All Illinois warnings.

Moderate

Nearest monitor

KNIGHT_P, 22 miles away (site 170650002)

Index measured

51 · Moderate

Measured at

Sun, 5:00 PM CDT

Fine particles

8.6 µg/m³

Ozone

58 ppb

Reporting area

St. Louis (Metro-east), IL, 61 miles away

Reported by

Illinois EPA

Area index

74 · Moderate

Measured, not modeled. AirNow observations are preliminary until the operating agency certifies them, which happens months later.

Illinois EPA's own forecast for St. Louis (Metro-east), written by a forecaster rather than read off a model.

NOAA’s National Air Quality Forecast Capability, bias-corrected against monitors, for this town’s own coordinate. The worst hour ahead is an index of 56, Moderate, around Sun, 3:00 PM CDT, from the run issued Sun, 7:00 AM CDT. This is a model, not a measurement.

Fine particles in micrograms per cubic meter, ozone in parts per billion as an 8-hour average. The index for each hour is EPA’s: the ozone figure is already the 8-hour average the ozone index is defined on, and the particle figure is run through EPA’s NowCast, which is how an hourly PM2.5 concentration becomes an index.

NOAA’s Hazard Mapping System analysts drew medium smoke over Mount Vernon in satellite imagery today (Sun, 7:00 AM CDT to Sun, 10:00 AM CDT). That is smoke seen from above; it is not always smoke at ground level.

NOAA’s model forecasts near-surface smoke peaking at 1.8 µg/m³ around Sun, 11:00 AM CDT.

Smoke on the radar over Mount Vernon

Moderate

Air quality is acceptable. There may be a risk for some people, particularly those who are unusually sensitive to air pollution.

Who is affected

People who are unusually sensitive to ozone or fine particles.

What to do

If you are unusually sensitive, consider making long or intense outdoor activity shorter or easier.

Index range

51 to 100

Category descriptions are the Environmental Protection Agency’s own.

What these numbers are. An index beside a monitor’s name is a measurement, published hourly by AirNow and preliminary until the operating agency certifies it. A category for today or tomorrow is a state or local agency forecaster’s own forecast for a reporting area. An hourly index is NOAA’s air quality model on a five-kilometer grid, not a reading from any instrument. Where a town has no monitor within reach, only the model figures appear, and the page says so.

The nearest towns with a page of their own, closest first.

• Ina, IL11 miles
• Wayne City, IL17 miles
• Sesser, IL17 miles
• Wamac, IL18 miles
• Centralia, IL19 miles
• Central City, IL20 miles
• Salem, IL22 miles
• Benton, IL22 miles

Observations and daily forecasts from AirNow, the US Environmental Protection Agency’s program with NOAA, the National Park Service, NASA, tribal, state and local agencies. Hourly forecasts from NOAA’s National Air Quality Forecast Capability. Smoke analysis from NOAA’s Hazard Mapping System. Alerts from the National Weather Service. Index categories and breakpoints are EPA’s, as revised in 2024.