Smoke returned to the Treasure Valley on Wednesday, but this time it came from the northwest.

Two fires burning near New Meadows and Riggins were settling down after heavy burning earlier in the week. But the Wesley and Sheep fires generated enough smoke to trigger a yellow, or moderate, reading on the Valley’s air quality index for Thursday morning.

Winds are expected to shift Thursday afternoon, providing relief once again.

“We’re looking for the winds to switch to the south,” National Weather Service meteorologist Valerie Mills said.

For most of August, Boise and other cities in the Valley sat under a shroud of smoke generated by the Trinity Ridge Fire in the mountains east of Boise, and desert fires in Oregon and Nevada.

But for the first 11 days of September, air quality was relatively good because the desert fires were out and the Trinity Ridge Fire had burned into past fires and diminished.

Some burning activity on the 146,000-acre fire was reported on its north end and in the Rainbow Basin on Wednesday, but it will return to a local command team Thursday.

At 1 p.m. Wednesday, several air quality gauges in the Valley were indicating pollutant levels in the moderate range, with the highest particulates recorded at Boise Fire Station No. 5 on 16th Street. Gauges in Meridian and Nampa were also slightly into the moderate range.

At about 1:30 p.m. Wednesday, smoke in Boise had reduced visibility to about 4 to 5 miles, according to the National Weather Service. Once again, the Foothills are obscured by the all-too-familiar haze.

The Wesley Fire near New Meadows has grown to more than 4,000 acres, and firefighters were building lines on its south end Wednesday to control an area where it had slopped over fire lines, fire officials said. The interior of the fire west of U.S. 95 burned a lot Wednesday.

“That’s what created all the smoke you have down there,” said Tracy Behrens, a fire information officer.

The wind shift might be good for Boise’s breathing but it will push the fire toward U.S. 95 and the riverside community of Pollack. Temperatures are expected to rise, and by Friday firefighters are expecting lower humidity that will pump up the fire.

The same is expected for the Sheep Fire, northwest of Riggins, which has grown to more than 21,000 acres and still threatens homes in several Salmon River tributary drainages. The Salmon River remains closed to boating from Lucile west to Twin Bridges, and the fire’s southern edge is U.S. 95.

Crews are still trying to keep the state’s largest fire, the 295,000-acre Mustang Fire, away from highways and homes, and they have been helped by the stable weather conditions.

Crews are mostly doing mop-up work on the 153,000 Halstead Fire around Stanley. Firefighters are still working to protect structures along Idaho 75 and up the Yankee Fork. This is another fire that burned into old fires and has become less fierce.

Smoke does remain a challenge for residents of Salmon and Challis from both the Halstead and Mustang fires.