Thursday was the Flathead Valley’s smokiest day in years, with school sports practices impacted, the mountains all but invisible and the sun bathing the region in an eerie light as it struggled to break through the haze.

A “very unhealthy” air quality alert was in effect for the Flathead Valley throughout the day, and Kristen Martin, an air quality meteorologist with the Montana Division of Environmental Quality, said that would likely persist over the next several days.

“‘Very unhealthy’ is basically when the general public should limit outdoor exercise and people with significant respiratory issues, such as asthma, should avoid all outdoor activity,” she said. “The general public will begin to have impacts from all outside activity, and will experience burning eyes and scratchy throats.”

The warning from the state forced local high schools to curtail athletic practices.

Glacier High School Activities Director Mark Dennehy said the cross-country team had just wrapped up its daily practice when the air-alert email came in Thursday morning and morning football practice wrapped up slightly early.

He said afternoon football practice was moved inside, where players would stick with shop talk and film studies.

“In actuality, this morning it wasn’t too bad out there,” Dennehy said. “We try to use the visual cues here around our facility. There’s a mountain range about four miles to the west, so if we can see that, it puts us in that area where we can practice.”

The Flathead High School football, soccer and cross-country teams were all forced to practice indoors because of the poor air quality.

Air conditions declined  throughout the day Thursday, and Martin said the particulate concentrations in the valley’s air were higher on Thursday than at any time in the last four years since the agency began continuous monitoring.

By noon, the 24-hour average particulate concentration was 82 micrograms per cubic meter, compared with 52 micrograms on July 18, 2014, previously the worst day.

The smoke is being pushed into the area by westerly winds blowing in from wildland fires in Eastern Washington, Idaho and Montana’s Kootenai National Forest. Martin said a particularly dense plume was visible from the fires raging in Washington, and any relief from an incoming cold front will likely be short-lived.

“It kind of depends on how much precipitation we get and how much the cold temperatures help decrease fire activity,” she said. “But it could be as early as Saturday afternoon — if we do get some improvement — that we’ll likely start to see hazy skies and smoke moving in again.”

While smoke in the valley was significant on Thursday, the air was still a long way from the worst air quality rating: “hazardous.”

“‘Hazardous’ is where everyone should avoid time outside, and especially time exercising outside,” Martin said. “But it’s unlikely given the concentrations we’re seeing that we’re going to reach those levels.”

Reporter Samuel Wilson can be reached at 758-4407 or by email at swilson@dailyinterlake.com.