Acalanes Ridge, California 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 Acalanes Ridge right now. All California warnings.

Good

Nearest monitor

Concord, 4 miles away (site 060130002)

Index measured

27 · Good

Measured at

Mon, 6:00 PM PDT

Fine particles

3 µg/m³

Ozone

28 ppb

Reporting area

Concord, CA, 5 miles away

Reported by

Bay Area Air District

Area index

31 · Good

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

Bay Area Air District's own forecast for Concord, 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 53, Moderate, around Wed, 8:00 PM PDT, from the run issued Mon, 5:00 AM PDT. 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 Acalanes Ridge in satellite imagery today (Mon, 1:00 PM PDT to Mon, 4:30 PM PDT). That is smoke seen from above; it is not always smoke at ground level.

NOAA’s model forecasts near-surface smoke peaking at 0.8 µg/m³ around Tue, 3:00 PM PDT.

Smoke on the radar over Acalanes Ridge

Good

Air quality is satisfactory, and air pollution poses little or no risk.

Who is affected

Nobody is expected to be affected.

What to do

It is a good day to be outside.

Index range

0 to 50

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.

• Walnut Creek, CAunder a mile
• Saranap, CA1 mile
• Waldon, CA2 miles
• Contra Costa Centre, CA2 miles
• Lafayette, CA2 miles
• Pleasant Hill, CA3 miles
• Alamo, CA5 miles
• Pacheco, CA5 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.