The Rim fire became personal for Fresnans on Friday when smoke from the massive blaze blew into town.
But while much of Fresno stewed in hazy conditions, the western and eastern sides of the Valley were not as affected, said Brian Ochs, a National Weather Service meteorologist.
The Rim fire has burned more than 200,000 acres near Yosemite National Park. Most of the smoke from that blaze -- one of the biggest in state history -- has been blowing northward away from the central San Joaquin Valley since it began Aug. 17.
But Ochs said downsloping breezes off the Sierra on Thursday night and Friday morning pushed the smoke toward Fresno and areas south.
He described it as a narrow band through the middle of the Valley, with the west and east sides of the region less affected.
At one point Friday afternoon, visibility at Fresno Yosemite International Airport was reduced to four miles. By comparison, Lemoore had 10 miles of visibility.
"There probably will be some smoke that drifts down (into the Valley) in the late night and early morning," Ochs said. "It's kind of hard to say when and how long that will last exactly. Basically, at least through the Labor Day weekend and likely into next week."
Ochs noted dense smoke advisories remain in place at Lake Tahoe and Reno, which have been hit hard by air pollution caused by the Rim fire.
For the latest air quality reports, check the San Joaquin Valley Air Pollution Control District's Real-time Air Advisory Network page.
Fresno Fire Department was called out to about 20 calls of smoke from residents worried that there was a fire burning in their neighborhoods. Capt. Brad Driscoll said those calls went to the 911 dispatch. Many of the calls were early Friday afternoon, he said.
"If it's a fire, we want to tell people not to hesitate to call," he said.
American Ambulance, which dispatches for several fire departments in Fresno County and ambulance companies in Fresno, Madera and Kings counties, said there was a surge in "smoke check" calls and an uptick in respiratory ailments.
On average, the ambulance companies get 45 to 50 calls a day for breathing problems. By 3 p.m., American Ambulance reported 34 calls for breathing problems.
"At this point, I wouldn't say a significant jump, but we've seen a spike," said Jaime Martin, director of communications for American Ambulance.
The San Joaquin Valley Air Pollution Control District advised that outdoor activities requiring considerable exertion be changed or moved inside.
The air district fielded calls from a half dozen schools in Fresno, said district spokeswoman Heather Heinks. "Most were needing some professional confirmation of what they thought they should do."
At of 3 p.m. Friday, air in southeast Fresno was classified as unhealthy for all groups by the air district. Air monitors in Clovis, central and north Fresno classified air as unhealthy for sensitive groups.
Regardless of the forecast, Heinks said, if the air appears unhealthy, it probably is. Air monitors don't pick up conditions in all parts of the city, and air quality could be worse than what is being reported, she said.
Smoke from fires produces fine-particulate matter (PM2.5), which can cause serious health problems, including lung disease, asthma attacks and increased risk of heart attacks and stroke.
Poor air quality caused Fresno Unified School District to cancel elementary school and middle school practices, games and outdoor activities. Indoor practices were unaffected.
High school athletics were not canceled. But Fresno Unified officials were monitoring air quality.
All Central Unified outdoor events Friday were canceled. But Central High's football games at Hanford went on, Hanford Joint Union High School District officials said.
Clovis Unified officials were monitoring air quality readings to make sure it was safe to play. The district canceled all elementary school practices as of 3:30 p.m. Friday after further consultations with the air district, spokeswoman Kelly Avants said. Freshman football games were delayed until 5 p.m.
School officials in Madera and Visalia said conditions were good there and the games went on as scheduled.
Coming in Sunday's Bee
Bee environmental reporter Mark Grossi talks to experts about how the Rim fire exploded into one of the biggest wildfires in state history.
Staff writers Mark Grossi, Marc Benjamin and Lewis Griswold contributed to this report. The reporter can be reached at (559) 441-6386, firstname.lastname@example.org or @CarmenGeorge on Twitter.