Alta, 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 Alta right now. All California warnings.

Good

Reporting area

Colfax, CA, 11 miles away

Reported by

Placer County APCD

Area index

50 · Good

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

Placer County APCD's own forecast for Colfax, written by a forecaster rather than read off a model.

Written by Placer County APCD for Colfax and filed with AirNow.

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 Fri, 12:00 AM PDT, from the run issued Thu, 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 analysts have not drawn smoke over Alta in satellite imagery today.

NOAA’s model forecasts near-surface smoke peaking at 2.1 µg/m³ around Thu, 6:00 PM PDT.

Smoke on the radar over Alta

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.

• Colfax, CA11 miles
• Nevada City, CA12 miles
• Foresthill, CA13 miles
• Grass Valley, CA13 miles
• Alta Sierra, CA14 miles
• Lake of the Pines, CA18 miles
• Meadow Vista, CA18 miles
• Penn Valley, CA20 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.