The San Joaquin Valley Air Pollution Control District has announced an alert in Madera County for smoke coming from the Junction fire near Oakhurst, south of Yosemite National Park.
Check the particles, known as PM-2.5, in your area on the air district's real-time monitoring page.
As weather conditions change, smoke impacts may be felt in other counties, air authorities said. The counties include Merced, Stanislaus, Fresno, Tulare and Kings.
If you see or smell smoke, you are likely breathing it. Smoke contains gases and particles that trigger health problems, such as allergies and asthma.
The tiny particles have been linked to chronic heart disease and early mortality.
The air district has a web site related to Sierra wildfires.