The areas referenced in the following bulletin from the the South Coast Air Quality Management District can be found on this interactive map. Altadena falls within Area 8.
The Williams fire is burning in the San Gabriel Canyon of the Angeles National Forest, north of Glendora (San Gabriel Mountains, Area 15). Full containment is not expected for several days. Through the day, most smoke will move into and over the mountains toward the north, with little smoke expected in the populated areas of the South Coast Air Basin below the mountains. Air quality in the San Gabriel Valley (Area 9) has remained in the Moderate range this morning. However, downslope overnight flows will likely bring smoke to the San Gabriel Valley (especially Area 9) into Wednesday morning, depending on fire and weather conditions and further containment.
Particulate matter air quality may reach Unhealthy for Sensitive Groups levels, or higher, in areas directly impacted by smoke. Areas of direct smoke impacts and Unhealthy air quality may include:
- portions of the San Gabriel Mountains Area (Forecast Area 15)
- the East San Gabriel Valley (Area 9) – mainly overnight and in the morning.
Surrounding areas below the San Gabriel Canyon, including the West San Gabriel Valley (Area 8) and the northern portions of the Pomona Walnut Valley (Area 10), may also experience periods of smoke overnight and in the morning. If this occurs, particulate matter concentrations may reach the Unhealthy for Sensitive Groups range in these areas.
In any area directly impacted by smoke: Everyone should avoid any vigorous outdoor or indoor exertion; people with respiratory or heart disease, the elderly, and children should remain indoors. Keep windows and doors closed or seek alternate shelter. Run your air conditioner if you have one. Keep the fresh air intake closed and the filter clean to prevent bringing additional smoke inside.