Moderate is not a term often used to describe the San Francisco Bay Area, but it is the key word this week when it comes to the region's air quality.
The Bay Area Air Quality Management District issued a forecast Saturday that calls for moderate air quality through at least Thursday (Dec. 2).
While moderate is not good, it's not bad either.
It also falls short of an alert, sitting smack dab in the middle between "good" and "unhealthy for sensitive groups" on the air quality index as measured by the Environmental Protection Agency.
There are three higher levels — "unhealthy," "very unhealthy" and "hazardous" — on the scale that measure progressively worse air quality.
The index measures pollutants, includes measures for six major air pollutants — ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide and two sizes of particulate matter — which are converted to numbers for each pollutant.
Anything below 100 should not affect health of the general public, according to federal officials, though readings in the moderate range of 50 to 100 may affect unusually sensitive people.
The local AQI forecast ranges from a low of 59 in the south central bay (the East Bay south of Oakland to Fremont and from Redwood City to Mountain View on the west side) to a high of 89 in the northern zone (Sonoma and Napa counties and the southeast section of Marin County).
The daily forecast is available by signing up for email AirAlerts or by calling the Air District's 24-hour, toll-free information line (1-800-HELP AIR).