Air quality in the Flathead Valley spiked to unhealthy levels over the weekend, and with wildfire activity across the West ramping up, more hazy days are ahead.

Data from air quality sensors showed that particulate matter peaked overnight Saturday into Sunday in the Flathead Valley before lowering to moderate levels Monday morning.

Air quality remained at unhealthy levels on Monday for Mineral, Sanders and Missoula counties. People in sensitive groups should avoid all physical outdoor activity when air quality is rated as unhealthy.

According to the Montana Department of Environmental Quality, prevailing winds are ushering in smoke from large fires in Idaho, Washington and Oregon. Meanwhile, multiple new fires in western Montana are adding localized impacts.

Northeasterly winds may help improve smoke conditions Tuesday across Northwest Montana, but west-central and southwest Montana will continue to see degraded air quality, according to the National Weather Service in Missoula.

High pressure remains in place through the rest of the week and into the weekend — meaning hot, dry and smoky conditions will persist.

MULTIPLE WILDFIRES burning on the Lolo National Forest in Sanders and Mineral counties are partially to blame for the local smoke impacts.

The West Lolo Complex was estimated at 1,017 acres Monday morning. The complex consists of seven lightning-caused fires near St. Regis, Thompson Falls, Superior and Plains. The Deep Lookout Fire east of Superior and the Thorne Fire near Thompson Falls were the largest in the complex.

About 220 firefighters were assigned to the area, including air resources, smokejumpers, ground crews, engines and heavy equipment.

Other nearby fires include the Henry Fire just outside of Plains, which was estimated at 130 acres on Monday, and the 200-acre Little Money 2 Fire southeast of Plains.

Meanwhile, three fires are burning on Lolo Pass west of Missoula, including the Lolo Creek Fire in the Missoula Ranger District and the BM Hill and Shotgun fires in the Powell Ranger District in Idaho. The three fires were being managed under the Granite Pass Complex Type 3 incident command.

The BM Hill Fire grew substantially Monday to 837 aces and was expected to merge with the 60-acre Lolo Creek Fire. The Shotgun Fire was about 50 acres and burning in heavy downed timber.

An evacuation warning was in place from the Idaho border to Lolo Hot Springs. According to the U.S. Forest Service, a limited number of firefighters was focusing their efforts on structure protection in the Lolo Hot Springs and Granite Hot Springs areas. The Lolo Pass Visitor Center was closed due to fire activity.